If you should find that you have created a PDF and then realized you maybe missed a few pages that are important, Acrobat offers a tool to add pages to a preexisting document. Unlike other publication programs, Acrobat is designed to create documents that are as close to a hard copy as possible, because of this you don't insert pages like you would in a publication program. To add a page, go to: Documents -> Insert Pages. You should see a browser window that asks you to locate the document you wish to add as a page. By default the browser only looks for preexisting PDF files, if you want to add documents from other programs, open the drop-down menu titled "Files of type:", and choose all files. Choose the document you wish to add as a page, then choose where you want this page inserted and hit OK. Acrobat will add your pages to the existing PDF.