Hi kita36726542 ,
Please try this step :-
Open the Document in Acrobat ,then go to Print Menu. Then got to 'properties' > Layout > Advanced > then from Paper Size option select the option for 'PostScript Custom Page Size'.
From there you may set the Page Size to 10x12 ,then select OK . Then on Clicking 'Print' will recreate he document with the size of '10x12'.
Let me know if it works.
Very bad idea!!
“Refrying a PDF” by printing to PostScript and distilling to get a new PDF is absolutely NOT an Adobe-recommended fix or workflow!
Besides the fact that this hack only works on Windows, it also has the potential of effectively ruining the PDF file since it eliminates color management, flattens transparency, and removes other optimizations that may be in the original PDF file! (Flattening transparency degrades quality and may interfere with the ability to properly search the document's text).
Also, Kit Anstey did not indicate whether they wanted to scale the file's contents, simply change the margins, or both!
To simply increase the page size and in this case increase the margins, the Set Page Boxes (Adjust visible page area) tool of Acrobat DC will accomplish this task. If you need to scale the content on the page, there is the Scale pages and Scale page content fixups in Acrobat Pro DC Preflight.