It's not really possible to talk about doing something on the iPad without talking about an app. In this case it has to be an App Store app, since none of the native ones can edit PDF files in any way.
PDF Expert will combine/copy/paste/delete pages in PDF files.
But if you've got a Mac handy (no idea how updated the cube can get) the Preview app in OS X is capable of combining PDF files. Well, the current and several versions back can. No idea what the version you are using can do.
For a professional(er) approach on a Mac, I've seen PDFPen recommended by bloggers I respect.
There might be some web app/site PDF editing tool that will do this, and work in Safari, but I have not idea. I vaguely recall some site like this. It would require you to upload the PDF files, do whatever, then download the results. The place to start looking for them would be on Adobe's site.
Good luck.