You would need to Ask the printer what they did and why the did what they did. Did the Printer ask you to provide a PDF? I would think most Printers would want a sRGB jpeg file from you.
Our process is to create the file in indesign, exported as a print PDF.
When I (like the printer) opened the PDF with Photoshop and I see that it auto changes the dimensions to a width of 270cm instead of the 390cm it should be.
How do you confirm the PDF page size?
I also opened it in illustrator just the see if document size was correct, and yes it was the right size in illustrator.
The issue is why did photoshop downsize the print PDF? Is there a file dimension limit when opening a PDF document in PS?
No, how did you check it in Acrobat? Did you check it in Acrobat? Until you've verified the size we don't know that Photoshop downsized it for sure. Could have resized on export.
It is the correct size in Acrobat.
Ok, then that is unexpected. Maybe you can share the file (or a sample made the same way) for others to verify...
I will break down the process and included a link to the PDF.
Created in indesign > exported as a press quality PDF 300dpi with bleeds and crops
Right clicked on PDF > open with Photoshop CC 2018 > Import options displays width as 270.93cm (which is wrong)
I also tried in the import options to change it from 270.93 to the correct size and I got this pop up error
"A number between 0.01 and 270.93 is required. Closest value inserted "
Link to PDF:
I took screen shots also attached below