Why is the page size different when i create a pdf from a mac word file

The maximum page size of a document in Word is 22x22 inches.

see: https://support.microsoft.com/en-us/help/95109/wd-maximum-page-size-of-a-document-is-22-by-22-inches ​

However, as you are using the Mac version of Word, the setting of the Page Size is actually done outside of Word as far as I can tell, which would explain why you could enter 48in as a measurement.

To verify this I did the following two tests.

Test 1 on Mac OS Office 365 version of Word:

• Changed Page Set-up to 12192mm (48in).
• Created a PDF.
• PDF size is 558.8mm (22in)

Test 2 on Windows Office 365 version of Word:

• When trying to create a Paper size of 12192mm (48in), I receive a warning.
• The measurement of the paper size must be between 2.6mm and 558.7mm (that's 22in!!).

Because the Page Setup in the Mac version of Word is actually set OUTSIDE of Word (the Size menu seems to be disabled in the Layout Ribbon), you don't get the error about the limitation of the document size.  However the Mac version of Word must silently adjust the size of your document to the maximum allowed size somehow (22in), which explains why when creating the PDF you end up with a 22in document.

• e.g.If you use File > Page Setup - I believe is part of Mac OS, NOT Word.