(From http://www.ubuntugeek.com/list-of-pdf-editing-tools-for-ubuntu.html)
Pdftk allows you to manipulate PDF easily and freely. It does not require Acrobat, and it runs on Windows, Linux, Mac OS X, FreeBSD and Solaris.
Examples
Merge Two or More PDFs into a New Document:
pdftk 1.pdf 2.pdf 3.pdf cat output 123.pdf
or (Using Handles):
pdftk A=1.pdf B=2.pdf cat A B output 12.pdf
or (Using Wildcards):
pdftk *.pdf cat output combined.pdf
Split Select Pages from Multiple PDFs into a New Document:
pdftk A=one.pdf B=two.pdf cat A1-7 B1-5 A8 output combined.pdf
Rotate the First Page of a PDF to 90 Degrees Clockwise:
pdftk in.pdf cat 1E 2-end output out.pdf:
Rotate an Entire PDF Document’s Pages to 180 Degrees:
pdftk in.pdf cat 1-endS output out.pdf
Encrypt a PDF using 128-Bit Strength (the Default) and Withhold All Permissions (the Default):
pdftk mydoc.pdf output mydoc.128.pdf owner_pw foopass
Same as Above, Except a Password is Required to Open the PDF:
pdftk mydoc.pdf output mydoc.128.pdf owner_pw foo user_pw baz
Same as Above, Except Printing is Allowed (after the PDF is Open):
pdftk mydoc.pdf output mydoc.128.pdf owner_pw foo user_pw baz allow printing
Decrypt a PDF:
pdftk secured.pdf input_pw foopass output unsecured.pdf
Join Two Files, One of Which is Encrypted (the Output is Not Encrypted):
pdftk A=secured.pdf mydoc.pdf input_pw A=foopass cat output combined.pdf
Uncompress PDF Page Streams for Editing the PDF Code in a Text Editor:
pdftk mydoc.pdf output mydoc.clear.pdf uncompress
Repair a PDF’s Corrupted XREF Table and Stream Lengths (If Possible):
pdftk broken.pdf output fixed.pdf
Burst a Single PDF Document into Single Pages and Report its Data to doc_data.txt:
pdftk mydoc.pdf burst
Report on PDF Document Metadata, Bookmarks and Page Labels:
pdftk mydoc.pdf dump_data output report.txt