Can I combine ADOBE PDF files?

I have many PDF file of book in which there are 4000 pages & the files are 400 .Is there any program that I can use to merge all of the files together to create an amalgam of the entire BOOK in series like page by page ?
Answer #1
Adobe Acrobat Pro 9.3.2 Extended
Click the “Combine” button
Select “Merge Files Into A Single PDF”
Click “Add Files” button
Select all the files you want to add (you can select them all at once and then sort if you like)
Click “Combine Files” button
Done
PS: Don’t use the new Adobe Acrobat X, it’s gay.
Answer #2
PDF Split and Merge
A free open source tool to split and merge pdf documents
http://www.pdfsam.org/
or google “merge PDF files” for other ways
that’s gona be a large book
if you have truble doing all at once try 40 at a time then merge the 100 new ones
Answer #3
ty guys it WORKS