MarkWahlstenDI

To add to @JohannaH's great list of resources, for anyone new to PDF accessibility and would like to know more:
AccessAbility 2: A Practical Handbook on Accessible Graphic Design | RGD  A good and brief overview of how typography, colour and language affect accessibility (digitally, and in print) It has some short guides for making accessible PDFs from InDesign or Word (+Acrobat) It also has a really useful section on how to convey the benefits of prioritising accessibility to bosses, stakeholders and co-workers As a side-note, the PDF document itself (now) also functions as a good example of tag structure and use of alt text  WebAIM: Alternative Text For me, alternative text (or alt-text) is frequently the part that stumps me the most WebAIM's guide gives a good outline of the "What", "When", "Where" and "How" of writing alt-text, with examples Accessible-PDF.info A good resource for troubleshooting! Last of all, my biggest (subjective) tip – sometimes the most accessible PDF may be no PDF at all... by which I mean:
Explore what the best format(s) for the digital output of your project is going to be, before defaulting to PDF: A well-structured HTML document is the gold standard for accessibility, and offers the most flexibility for users to tailor the content to their specific needs A "reflowable" EPUB3 is basically a portable HTML document For your content, there may be fewer steps involved in making a well-structured and accessible HTML or EPUB3 document Tools for creating accessible HTML and EPUB3 documents are far more widely available (and free) As a user-friendly way for writers to generate structured HTML documents from plain text, consider incorporating Markdown – as used by the online tool AROW, for example Not everyone can afford a subscription to Creative Cloud (or even Acrobat Pro on its own)! Only share information as a PDF if you absolutely have to ...and provide the important information in an alternative format, such as – you guessed it – HTML and/or EPUB3 Not to say PDFs aren't useful (they're not going anywhere) – but asking this question at the beginning could save you a lot of unnecessary headaches later.
Also – as @JohannaH highlighted, and many weary PDF remediators will tell you – Acrobat Pro and InDesign / QuarkXpress / MS Word don't represent the best, simplest, or most intuitive processes for creating accessible documents. They are just the least-worst tools available, and these are just useful guides for making the most of them Keep pushing for better tools!

I grew weary of waiting for Affinity to comment in this thread, so I contacted support directly. Here's the reply I received this morning:
To me, this translates as, "We hear you, and we don't care. Don't hold your breath."

Fully agree!
Look at what Will said. In any case, the functionality that is missing is exactly what all users have been screaming for over the past years (not only ePub, but for example footnotes/endnotes). If you provide similar functionality and drop the "old " version, you are "replacing" it, like it or not, even if it is not exactly the same. And then you should have the main features (not the same code!). You can add new features and drop unused or unnecessary ones. And BTW, you only inherit the bloat and bugs only if you reuse the code, but that is NOT what we are talking about - we are talking about features, not reuse of code!
For your information, I have over 40 years of experience in software development (I started with punch cards!). I have developed desktop software, websites, corporate systems and even airborne software operating systems for fighter aircraft. I have also chaired two international software standardization committees, so I need to take no lessons from anybody.
Having stated that, and having also developed consumer software, when you drop a product and replace (YES, replace) it by something oriented to the same purpose, the users expect something similar or better. You can develop it from scratch (no objection to that), but you should take care that you include the features that your users value. The very first thing that we did when we developed consumer software is ask the users what features they considered essential/valuable, and made sure that those were included. This is not discrediting anyone's work - but ignoring the users and what they require is simply sloppy and is unlikely to increasy user satisfaction. Anyone with a minimum of knowlege in marketing will tell you that user satisfaction is key to the success of a product.
It is evident that you are NOT a software designer, because otherwise you would know that the backwards compatibility of old files is not necessarily maintained even over different versions of a same software. Plenty of examples abound. And you are insisting on code, as if code portability and code reuse was the only solution when you want to create a new product or even a new product version. Let me tell you something: I completely redesigned with my team a major application that had been initially developed in Powerbuilder to C++. Significant architectural changes had to be done, and except some very few algorithms, NOTHING was reused (zero code ported). Yet it was marketed as the new "modern" version of the SAME product! (and yes, we created it from scratch.) Backward compatibility? None. We had a way of migrating the old data (by means of a conversion program), but there was no way to run the old files/databases, nor get back to the old format. It simply made no sense to maintain backward compatibility, and still it was a new version of the same application!

Can we have EPUB export please?

Just had a chat with my hubbie. He prepares all the online PDFs for work, does all the tagging etc and on his work laptop has accessibility checker software for highest tier. He told me to just give him my finished patterns on Affinity, send it to him and hell put it through his Acrobat writer at work and then through their accessibility checker software and manually check it himself and write tagging for me, correct anything I've done incorrectly. I just have to ensure no tables, full explanations of pics and diagrams included and he'll tag those for me. He'll ensure I don't end up with those nesting errors or style inconsistency problems etc. I am also talking to several knitwear designers who run accessibility checks for usability which is basically the type of instructions that you give knitters that differ from knitters with high vision. There is a Worldwide database of low vision knitting patterns and when you load one up, a checker has to approve them too. Obviously I'll try to get it right but if they get thrown off at least I know what to correct. I've seen some people get really offended if their pattern gets 'rejected' for non compliancy and other people commiserating with them 'I'm so sorry you have to go through this, its not fair' etc and I'm thinking why? If its not right, its not right, and you go back and fix issues. It's not a personal attack it's a requirement for access. And some people say 'well I tried my best, and THEY don't like it, that's all I'm doing. I don't have to do this'

I have been trying to get my head round tagging for Headers. I wish that Header styles in Affinity could do that, I have been creating them in a logical order, but not sure how to tag it without using html. As a person with no profession or business, its quite a stretch. I can't type or navigate that well, have a hand disability and visual issues myself and tolerate about 15 mins screen time in one sitting. Thank God for speech to text. I don't know html. I am just hoping to write up two pdfs for charity, and I haven't worked for almost a decade. If I had Acrobat would I be able to tag in that? Or in Affinity itself? There's an additional problem not just how it reads etc, but in the fact knitting instructions are standardised and don't get recognised as language. But the industry requires those standard abbreviations which vary for each country and that is even between English speaking countries. Can I tag that as normal text, if its where you put the normal text? And there's pacing in how it is read out, is there a way of getting a screen reader to do a longer pause or maybe stop at the end of a line? Can I get any tag in there to tell a screen reader to just go back to beginning of one line? Someone will have to write some software for navigating a knitting pattern it is not like a normal PDF and isn't used passively like reading is. If knitters with visual impairment can't grasp an instruction, or make a mistake, they might need to rip work out and go back a row or a round, or it could become confusing. I am putting in Row or Round numbers can they be tagged for a search?
There is a lot I do not know....

@erssie, you could try the Pave website to change the PDF that Affinity produces into an accessible one. 
https://pave-pdf.org/?lang=en
They offer a free online tool which might be the best option for you.
Accessible PDF's is more than just the alt-texts. You'll need tags so a screenreader can easily read the text. If there are any headings, lists or tables in it the tags will show that to the screenreader, just like on a website. Even if your blind group members tell you it's fine without them it still might cause a problem when someone uses a different PDF reader. Pave should be able to fix that for you.
To check the PDF when it's finished the also free PAC tool might help. It's what most people working in accessibility use to check PDFs.
https://pdfua.foundation/en/pdf-accessibility-checker-pac/register
This tool is simple to use, but make sure you read the manual to understand the outcome. Just ask here if you have questions and I'll try to help, because I don't think you'll need to fix everything that PAC shows as a fault. It's a bit too strict.

I'm not a company, I'm just little ol' me but I design knitting patterns for charity. Some of them include charts and diagrams. Blind people do knit but those charts/diagrams are often inaccessible. I've just spent a few very long days translating a charted design into line by line instructions for knitting the stitches, and in my rough pattern in Word I have my alt text descriptions on my photographs etc. Word creates a pdf that my blind knitting group have told me is working with alt text on the photos etc. I would now like to lay that out in Affinity Publisher, was struggling as I am new to it, and could not find a place to put a text description of a photo, so have ended up here. I still want to do my work in Affinity Publisher and would like to avoid using Adobe products although i have a free Acrobat Reader DC. I understand that Affinity is not going to give me an accessible pdf as far as trying to put alt text to my photos, which is a shame. But if I create a PDF from Affinity, will it be editable by any editor to add the descriptions on photos afterwards to comply with various screen readers or Read Aloud software? And does that mean Id have to subscribe to a PDF Editor. I have spent days and days, with a hand disability and needing a lot of support, to try and make my patterns accessible. I'm willing to do what it takes, and I am not a company just an individual, but its frustrating to not find the tools to do so. And I cannot afford Adobe subscriptions or other ones out there, which is why I purchased Affinity. I was going to volunteer as well, free of charge as I work so slowly with my disability, to translate others knitting patterns or craft literature into accessible documents so that people with impaired vision can easily listen to instructions and knit along at the same time. I'm scared that I might get prosecuted in the future for doing that if I don't have the right tools. It'd be a crying shame if I have to go from doing my own layouts to just using Word again. That is an awkward thing to use, I hate it. I'm already complying with regards to text size, type and layout to standards set for knitwear designers, its just the alt text thing I can't do. I also cannot afford to pay accessibility editors to do it as I am volunteering anyway.
Can someone tell me where after Affinity they are going to put their alt text on? And if its not available automatically, can I just put a readable caption below/or above the photo in line with it for it to be read out? 

Just a short note to warn once again that InDesign is not able to generate, on its own, a perfectly accessible PDF file. Further editing with Adobe Acrobat (Pro) is required.
When checking in Acrobat 2020 a file generated from InDesign, I get the attached report. Some of the missing features are to be added in Acrobat; some others require manual processing.
It would obviously be highly desirable if Publisher 2 included the features requiring Acrobat in an InDesign-based workflow. Let's hope this is possible…
Paolo
 

The Accessibility Checker in Acrobat, usually returns “errors” on items that need manual checks. This table in PaoloT post shows areas that the “designer” failed to initiate in the overall structure of the document. Besides Acrobat DC. There are other tools available (especially in the Windows world) that will remediate documents. 
At this point in time Affinity Publisher does not do this.
Most screen readers require a structured document in order for them the provide “accessibility”. They do this via “tags” and these tags are part and parcel of an extensible markup language (the subset is hypertext markup language, which is used in ePubs). Tags, document structure and tab order have to be in sync. 
MS Word has rudimentary document structure, and tags implemented through Character and Paragraph styles (same as InDesign).  
MarkWahlstenDI makes strong points in his post above... 
At this point in time Affinity Publisher does not do this.   Also Photo and Designer will need to add alt text descriptions to images.
 

To add to @JohannaH's great list of resources, for anyone new to PDF accessibility and would like to know more:
AccessAbility 2: A Practical Handbook on Accessible Graphic Design | RGD  A good and brief overview of how typography, colour and language affect accessibility (digitally, and in print) It has some short guides for making accessible PDFs from InDesign or Word (+Acrobat) It also has a really useful section on how to convey the benefits of prioritising accessibility to bosses, stakeholders and co-workers As a side-note, the PDF document itself (now) also functions as a good example of tag structure and use of alt text  WebAIM: Alternative Text For me, alternative text (or alt-text) is frequently the part that stumps me the most WebAIM's guide gives a good outline of the "What", "When", "Where" and "How" of writing alt-text, with examples Accessible-PDF.info A good resource for troubleshooting! Last of all, my biggest (subjective) tip – sometimes the most accessible PDF may be no PDF at all... by which I mean:
Explore what the best format(s) for the digital output of your project is going to be, before defaulting to PDF: A well-structured HTML document is the gold standard for accessibility, and offers the most flexibility for users to tailor the content to their specific needs A "reflowable" EPUB3 is basically a portable HTML document For your content, there may be fewer steps involved in making a well-structured and accessible HTML or EPUB3 document Tools for creating accessible HTML and EPUB3 documents are far more widely available (and free) As a user-friendly way for writers to generate structured HTML documents from plain text, consider incorporating Markdown – as used by the online tool AROW, for example Not everyone can afford a subscription to Creative Cloud (or even Acrobat Pro on its own)! Only share information as a PDF if you absolutely have to ...and provide the important information in an alternative format, such as – you guessed it – HTML and/or EPUB3 Not to say PDFs aren't useful (they're not going anywhere) – but asking this question at the beginning could save you a lot of unnecessary headaches later.
Also – as @JohannaH highlighted, and many weary PDF remediators will tell you – Acrobat Pro and InDesign / QuarkXpress / MS Word don't represent the best, simplest, or most intuitive processes for creating accessible documents. They are just the least-worst tools available, and these are just useful guides for making the most of them Keep pushing for better tools!

Hello! I am also waiting for news from SERIF about accessibility in Affinity Publisher. Thanks! 

To add to @JohannaH's great list of resources, for anyone new to PDF accessibility and would like to know more:
AccessAbility 2: A Practical Handbook on Accessible Graphic Design | RGD  A good and brief overview of how typography, colour and language affect accessibility (digitally, and in print) It has some short guides for making accessible PDFs from InDesign or Word (+Acrobat) It also has a really useful section on how to convey the benefits of prioritising accessibility to bosses, stakeholders and co-workers As a side-note, the PDF document itself (now) also functions as a good example of tag structure and use of alt text  WebAIM: Alternative Text For me, alternative text (or alt-text) is frequently the part that stumps me the most WebAIM's guide gives a good outline of the "What", "When", "Where" and "How" of writing alt-text, with examples Accessible-PDF.info A good resource for troubleshooting! Last of all, my biggest (subjective) tip – sometimes the most accessible PDF may be no PDF at all... by which I mean:
Explore what the best format(s) for the digital output of your project is going to be, before defaulting to PDF: A well-structured HTML document is the gold standard for accessibility, and offers the most flexibility for users to tailor the content to their specific needs A "reflowable" EPUB3 is basically a portable HTML document For your content, there may be fewer steps involved in making a well-structured and accessible HTML or EPUB3 document Tools for creating accessible HTML and EPUB3 documents are far more widely available (and free) As a user-friendly way for writers to generate structured HTML documents from plain text, consider incorporating Markdown – as used by the online tool AROW, for example Not everyone can afford a subscription to Creative Cloud (or even Acrobat Pro on its own)! Only share information as a PDF if you absolutely have to ...and provide the important information in an alternative format, such as – you guessed it – HTML and/or EPUB3 Not to say PDFs aren't useful (they're not going anywhere) – but asking this question at the beginning could save you a lot of unnecessary headaches later.
Also – as @JohannaH highlighted, and many weary PDF remediators will tell you – Acrobat Pro and InDesign / QuarkXpress / MS Word don't represent the best, simplest, or most intuitive processes for creating accessible documents. They are just the least-worst tools available, and these are just useful guides for making the most of them Keep pushing for better tools!

+1 for this feature request.  We just got burned because an Affinity Publisher document was not compliant.
See also this post:  https://www.reddit.com/r/Affinity/comments/j2fq0w/accessibility_regulations_forced_me_to_switch/
Serif:  Please address this feature request sooner rather than later.

I've been just looking up the accessibility features for PDFs created in Affinity for a client, and I'm so surprised that this is the only post about it!

I've completely convinced my client to go with Publisher over InDesign, but this one feature may be a deal-breaker that'll force us to go with InDesign. It's not just government documents that need accessibility features, accessibility is a major ethical component for many consumer-facing brands who are demanding this with their websites online and in other digital documents. Affinity, please look into this!

Agreed, this is a rather pressing issue for me to solve and I only have Affinity.

I'm going to throw my support in for this feature. I work for a U.S. university, and every printed document that we put on the web has to be accessible. inDesign's workflow for this is tedious and uncertain, while Acrobat has me pulling my hair out every time someone hands me a document to be made accessible. 

I agree, would love to see Affinity push some updates to Publisher for accessibility. I feel Affinity can become a game changer and disrupt the publishing world if they can incorporate really awesome accessbility features from tagging elements, tables and reading order.

@Chrysogonus - agreed.
Accessibility is now a legal requirement in the UK for public sector websites (even for very small public sector bodies who struggle to afford Adobe software).
This includes any PDFs on the websites.
Even MS Word now has an option to save an accessible PDF.
 

Agreed. It would be a good feature to have. Some of my clients have recently been asking for this, and InDesign certainly does not make the job easy or fast.

I totally agree. I don't know many designers who even know it's possible to create an accessible PDF, or what it actually means. But everyone gets it for web work. I can't see a single disadvantage of PDFs were created to be accessible by default.

I'd love to see Affinity Publisher support tagged and accessible PDFs from the ground up, ideally with full support for PDF/UA. Many institutions and government bodies require this for public documents, and making it part of the program's logic could be a major selling point.
I am not convinced that the way in which InDesign implements this in is the best way of going about it; it tends to create a lot of extra work that most people don't bother with. Instead, it should be possible to use this structural information to make document creation more efficient and improve a print/Web workflow.

+1 for accessible PDFs. 

Adding my voice to this! I also 100% agree with @MaggieP's comment.
Accessible PDFs, or accessible ePub3 creation is vital for digital content creation. It is a strict legal requirement for online documents in many countries, not to mention common-sense from a basic communication point of view.
How can we call ourselves effective content creators, if we keep ignoring a whole chunk of our target audiences?