Do you have multiple single page PDF files that you'd like to convert into one larger multiple page PDF document? This is something that comes up a lot in the NMC, and here's how you do it:
1) Open the first page in Acrobat Professional
2) Document --> Insert pages
3) Select the next page to be inserted, and tell Acrobat where to put it (before/after the current page, at the beginning/end of the document, etc).
4) Repeat until all pages are added.
5) Save As for the new document.