Newbie question about PDF export

[Ben M]

I'm currently tinkering with settings to try to reduce the size of my PDF export.

I have the same graphical element (a logo) repeated ~200 times in my project. Do I need to do anything to make sure that it's just being encoded once and referenced 200 times in the output PDF, rather than bloating the file size by encoding multiple copies?

Each instance is a linked image, and most of them don't have adjustment layers, if that matters.

[walt.farrell]

As I understand it (mainly from reading the forums, not personal investigation and examination of internal PDF contents):

• There are no options for you to set.
• The Affinity apps will embed your item multiple times, and this will bloat the output file with the multiple copies. I thought there was a forum thread discussing this, but I can't find it right now.

[Ben M]

That was what I was worried about. But I just did some tests with a new five-page document and they suggest it's reducing images to a single encoding in a trivial case.

One placed image file, other pages blank => exports as 5074 KB PDF
Five placed copies of one image file => exports as 5075 KB PDF
Five placed copies of one image file, plus transforms/adjustments => exports as 9265 KB PDF
Five near-identical image files => exports as 15066 KB PDF

That makes me optimistic, but I'm not sure how I would check that this behaviour generalises to my actual project. Presumably by inspecting the output PDF with some tool.

 

[R C-R]

4 hours ago, Ben M said:

That makes me optimistic, but I'm not sure how I would check that this behaviour generalises to my actual project. Presumably by inspecting the output PDF with some tool.

What about just comparing the export file size with a version of your document with vs. without most of the 200 logo copies? You did not say if you are using master pages with the logo on a master page, but if you are it should be fairly easy to remove the logo from all the document pages & then place it directly on a few of the document pages.

[Ben M]

12 hours ago, R C-R said:

What about just comparing the export file size with a version of your document with vs. without most of the 200 logo copies?

Good idea. They're not inherited from master pages, but I deleted the copies through the resource manager to see the effect.

• Exporting at 98% jpeg compression, the PDF size is reduced by 9 MB (<1% change).
• Exporting at 85% jpeg compression, the PDF size is reduced by 4 MB (<1% change).
• I also tried re-linking them all at once to a copy of the source image file, and that had no effect.

So it's not really clear, but I'd lean towards the small changes suggesting they're being encoded sensibly in the PDF.

I was curious so I tested a few other things. At least with new documents, Publisher was very consistent in only marginally increasing exported file sizes with lots of extra duplicated images. It's also pretty agnostic to a lot of things like transforming the graphics, text overlays, etc. Exactly what you'd hope.

The biggest effects appeared when I had duplicate images overlapping other graphics (as opposed to e.g. appearing next to them). I am generating PDF/X which flattens transparency, so my guess is that for each such overlap it flattens/rasterises and encodes the resulting graphic in the PDF, replacing what would otherwise be a reference to a graphic it has already encoded. That might explain why in my project, the file size is still reduced a bit by deleting most of the duplicate logos.

Pragmatically though, however they're being encoded, the logos aren't contributing much to the large file size compared to other parts of my document, so I'll stop worrying about it.