I am trying to take a pdf I created on another app and adjust the margins proportionally. I'm ok if the text and images get smaller. I just need to have 1 inch margins. I feel like this should be a really simple thing but I've googled and searched for different apps and tried a million things in both illistrator and acrobat and nothing seems to work. Unfortunately I can't change the margins in my original file since the program I'm using just wont let me do it the way I would like without messing with a bunch of formatting.
Also, is there a reason i can't use the global edit tool on pdf links in illistrator?
PDFs are quite specific since the format isn't really meant to be editable to begin with. Changing the artboard size and re-saving your document should work, though, just as should assing it to a suitably sized canvas using the File --> Place function rather than opening it directly.
"Also, is there a reason i can't use the global edit tool on pdf links in illistrator?"
Yes, because it's a link, not the actual art.
You should be able to click on the linked pdf and choose Edit Original button in control strip, but you're then opening a pdf in Illy which is not a pdf editor, so your mileage may vary...
What is the "other" program you are using?
Just Place (Link) the PDF into a new Illustrator or InDesign document and scale it to get the size of margins you want, then re-PDF the new document.