Is it possible to join two single pages in a pdf into one double page spread?

Kevin

All you need to do is add the one PDF to the other PDF so that you have a two page pdf. If you have Acrobat 8 or Acrobat 9 (you failed to mention the version ) then you do a file > Print and in the Page Scaling options choose Multiple Pages Per Sheet. Pages per sheet choose 2. Then choose the Adobe PDF Printer as your printer and choose Print. This will create a letter size page with both pages on one sheet.

Thanks guys, that's what I was going to do but my boss insisted you can do it in acrobat.

The InDesign method Steve mentions is the best option. You can also place it in Illustrator as an import but you'll need to have the same fonts as the PDF file. This option will allow you to edit the files, pending what objects are editable. It will have a few quirks, and the text lines might be separate objects.

I'd go InDesign, but just in case you don't have ID, you can use Illustrator, but be prepared for a little work.

Place them into InDesign on two side-by-side pages, and create a PDF file.