Also I think it may be possible to directly edit the pdf in a text editor to change the page size how you need it.

If you open the PDF file up in notepad, search for: MediaBox[ 0.000000 0.000000 612.000000 792.000000] - that's what actually defines the page size.

Those are in "points" units where 1 point = 1/72 of an inch. So for a 18" x 32" page you want that to say: MediaBox[ 0.000000 0.000000 1296.000000 2304.000000] - that's 18 * 72 and 32 * 72.

Some areas of a PDF file can't be edited with new inserted digits like that because some things are based on byte offsets from the start of the file. But for this particular thing I think it comes after all that type of stuff so I think this particular direct edit should work, it seems to be ok over here. It might not be a bad idea to slice off one of the trailing zeros after the decimal point for those 2 edited values so the file byte length stays the same.

Anyway that could be another alternative to using Illustrator for the time being.

- Michael