pdfk is a swiss army knife for manipulation pdf files. No fancy GUI here so if you're comfortable with using the command line then you'll be happy with this one.
* Merge PDF Documents
* Split PDF Pages into a New Document
* Rotate PDF Pages or Documents
* Decrypt Input as Necessary (Password Required)
* Encrypt Output as Desired
* Fill PDF Forms with FDF Data or XFDF Data and/or Flatten Forms
* Apply a Background Watermark or a Foreground Stamp
* Report on PDF Metrics such as Metadata, Bookmarks, and Page Labels
* Update PDF Metadata
* Attach Files to PDF Pages or the PDF Document
* Unpack PDF Attachments
* Burst a PDF Document into Single Pages
* Uncompress and Re-Compress Page Streams
* Repair Corrupted PDF (Where Possible)
Runs on Windows, Linux, Mac OS X, FreeBSD and Solaris.
http://www.pdfhacks.com/pdftk/
Kate