Keeping exact file dimensions (mm) when exporting a PDF from Affinity Designer and opening it in Illustrator

[Nicolò]

Hi, 
I am designing some stickers for a car livery. I placed a render of the car in Affinity Designer, scaled it with the Measure Tool and now I have all of the stickers on the car with the correct size in mm. 
I need to have the stickers cut by a copy shop which uses Illustrator and I would like to copy all of my stickers into a file and send it to them in the correct size. 
The issue I have is that whenever I export a the PDF from Affinity and open it in Illustrator, none of the sizes are correct. 

Is there a way to have Illustrator keep the exact scaling from Affinity Designer?

Thanks for any help anyone can offer.

[David in Яuislip]

I don't have designer but if I draw some shapes in photo with the document dpi set to 96 then the sizes are pretty good

eg 1080x580mm becomes 1080.000944 x 579.998417 mm

[Nicolò]

Maybe I am missing something, but I have a 150mm high text in Designer turning into 95mm in Illustrator.

[walt.farrell]

1 hour ago, Nicolò said:

Maybe I am missing something, but I have a 150mm high text in Designer turning into 95mm in Illustrator.

Are you using 96 DPI as David suggested?

[David in Яuislip]

I get 95.997889 mm if the document is 150dpi

Try the attached, look at the 0 in the ttext as curves, it's 150.001111 mm here

dimns96.pdf

[Nicolò]

I tried David in Яuislip's file and also designed a similar test. They both work. However, my car livery file always loses some mm. Any idea why?

 

Also, I tried copying a text from the car livery document to another blank document and the dimensions are also changing within Affinity Designer. It is an issue of the Measure Tool?

 

[walt.farrell]

8 minutes ago, Nicolò said:

Any idea why?

Again, what DPI is it using?

[Nicolò]

I've set 96 on everything

 

[Lee D]

@Nicolò Are you able to DM me a copy or download link to your file so I can take a look?