Publisher – wrong trimbox dimensions

[petrchutny]

Hello,

I am trying to export a book in Publisher for the printer. The dimensions are set to mm, and the page size to A5. However, after exporting, the printer got back to me with the complaint that the dimensions aren't clear 148 x 210 mm, but actually 148.08 x 210.06 mm.

I have seen a few threads about this topic in the past, with no satisfying resolution, solution or answer - that would create hope in me, that I will be able to solve this issue, and give the printer what they ask for.

I feel quite dissatisfied that I have paid for a professional book setting software and cannot export a proper print PDF with a proper Trim box.

I know that Affinity by its nature operates in pixels, but I would expect that it will be able to set the trimbox somehow "over this" foundation, because it really matters to the printers.

Any advice please?

[Lee D]

@petrchutny We have an issue logged with our developers regarding PDF export sizes needing to be exact. You can try the following to see if this helps as a workaround for the moment.

Open Document Setup panel, change the Document unit to 'pixels', adjust the dimension size by removing any decimal pixels. Then change back to the unit you prefer and export to PDF.

[petrchutny]

Thanks @Lee D. The printer accepted the fraction of milimeters in the end. I will remember your advice, thanks.

[Oufti]

On 4/10/2025 at 8:43 AM, petrchutny said:

The dimensions are set to mm, and the page size to A5. However, after exporting, the printer got back to me with the complaint that the dimensions aren't clear 148 x 210 mm, but actually 148.08 x 210.06 mm.

The explanation is that you defined your document in mm where Affinity uses internally pixels and Adobe PDF uses points (exact fraction of an inch).
When the size is not an exact number of pixels, there is a rounding at export that slightly modifies the size. The fact that it's always rounded to the top can trigger some alerts in automatic flows since size exceeds the intended one, even if it's by less than an hair width. 

Compare first and second line of this table (before and after rounding): grey cells are rounded by excess.

 

Note: If you want the size in mm to always be an exact number of pixels (so that there won't be any rounding), you need to use a multiple of 25,4 for your document resolution (Document setup > dpi, where "dpi" stands for "number of pixels per inch"). For example, use 304,8 dpi instead of 300.

[petrchutny]

Thanks @Oufti! That's a great explanation right there. And great solution to this problem – I will remember it, thank you very much  

[Oufti]

On 5/7/2025 at 7:00 PM, Oufti said:

you need to use a multiple of 25,4 for your document resolution (Document setup > dpi, where "dpi" stands for "number of pixels per inch"). For example, use 304,8 dpi instead of 300.

Actually, it seems difficult to use this workaround since resolution is also eventually rounded to an integer value…

 

[user_0815]

Maybe you can substract the oversize from the bleed...

I had 0.03mm too much in the vertical dimension. 55.03 mm insead of 55 mm. So I set the bleed from 3mm down to 2.985 mm (3 minus 0.015 mm). The export now shows exact 55mm. 

My print shop accepts oversize because he requires a "minium" bleed instead of an "exact" bleed. So I can't verify whether this workaround actually works in practice for those who need the exact dimensions.

 

[Alfred]

46 minutes ago, user_0815 said:

My print shop accepts oversize because he requires a "minium" bleed instead of an "exact" bleed. So I can't verify whether this workaround actually works in practice for those who need the exact dimensions.

It seems crazy that any print shop should require an “exact” bleed, given that the whole point of having a bleed area is that trimming is intrinsically inexact. The standard metric bleed amount is 3 mm (0.118 in) and the standard imperial bleed amount is 0.125 in (3.175 mm).