PDF exporting at wrong size in both Illustrator and Indesign

[tanyacreates]

I'm trying to export an A4 artboard to an A4 PDF in illustrator. I'm not using a large artboard - I used the A4 preset like I always do. I've been using illustrator for years and never had this problem before. 

I have checked the artboard size is correct and I've checked all the settings I can think of.

When I export the PDF (either by 'Save As',  'Save As Copy' or 'Export for screens') it ends up being around 10% smaller than my document settings. 

When I open the PDF again in illustrator it is the correct size. But when I view it in Adobe Acrobat or Preview it is around 10% smaller. 

When I export it as a PNG it is the correct size. 

I also tried to import the pdf to indesign and when I exported it there I got the same issue. 

I have a client waiting for the correct sized artwork and a bunch more work due this week so I really need to get this sorted ASAP. Can anyone help?

[tanyacreates]

Just wanted to add I don't have any bleed on the file. 

[Ton Frederiks]

@tanyacreates Looks like a large canvas document. Although the canvas may be large, it can still contain smaller artboards like an A4.

Can you test that by zooming in or out to the maximum/minimum value?

A regular canvas can zoom in to 64000% and zoom out to 3,13%.

A large canvas can zoom in to 6400% and zoom out to 0,31%

If it is a large canvas, create a new document. Select the Print Presets and choose A4.

Copy your content and paste it into your new document (there is no way to convert a Large Canvas into a regular one).