From PDF Labs:
If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a simple tool for doing everyday things with PDF documents.You can 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,and 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)
What's new in this version:
Added drop_xmp output option for removing the document XMP metadata stream from a PDF.
Added dump_data output of custom page data embedded by STAMPtk tool. See the embed option in STAMPtk for more information.
Improved PDF bookmark merging logic so it can handle more input cases.
Fixed a password bug where some 'upper-ASCII' characters weren't being mapped to the correct code points.
Fixed a 40-bit decryption bug introduced in version 2.00.