OS X allows you to create PDFs from the standard print dialog in any application. There are some special steps necessary to create poster-sized PDFs:
- Go to File->Page Setup
- Under "Paper Size " select "Manage Custom Sizes "
- Click the "+" button at the bottom of the list of custom sizes. Double-click on the new "Untitled" entry and rename it to "36x44"
- While "36x44" is highlighted in the custom size list, change the "Page Size" settings to "Width" of 36 in, "Height" of 36 in. Set all "Printer Margins" to 0.
- Click "OK"
- Under "Paper Size" select the preset you just made
- Click "Ok"
- Go to File->Print
- Click the "PDF" button and select "Save as PDF"