After made iText worked on Google App Engine, I built Another application, Remove PDF Password Online. It bases on iText 2.1.7 but with many modification.

the main features of pdfdecrypt online are,

• remove restrictions on any secured PDF document (you should have the right to do it, for example, if you forgot the password). Any Acrobat version up to 9 is supported, even with 128-bit AES or 128-bit RC4 encryption. PDF restrictions removal is an instant process. Unlocked file can be opened in any PDF viewer without any restrictions so you may edit/copy/print it.
• remove the PDF open password. Decryption of the file with password for opening is guaranteed for PDF files Any Acrobat version up to 9 is supported, even with 128-bit AES or 128-bit RC4 encryption,but you must know the password first.

It supports upload PDF documents from your disk and give a PDF url.

If you like it, just have a try now, it is free.

PdfCrypt is a windows 32 console/command line version PDF encrypt & decrypt software, supports standard 48 bits, 128 bits, AES-128 bits encryption, and decryption. And first of all,it is free.

Download now(1.84M).

If you need java source code, linux stand alone version, or .net version, please let me know.

It bases on modified version iText 1.5.4 and gcj 3.4.2, compressed with UPX 3.03.

Here is the usage manual,

usage:
pdfcrypt

Where:
= encrypt
[info pairs]

= decrypt

permissions is 8 digit long 0 or 1. Each digit has a particular security function:

AllowPrinting
AllowModifyContents
AllowCopy
AllowModifyAnnotations
AllowFillIn (128 bit only)
AllowScreenReaders (128 bit only)
AllowAssembly (128 bit only)
AllowDegradedPrinting (128 bit only)

Example permissions to copy and print would be: 10100000

Some example,
pdfcrypt encrypt in.pdf out.pdf owner_pwd user_pwd 10100000 AES
pdfcrypt encrypt in.pdf out.pdf owner_pwd “” 11100000 128 //128 bits encrypt with owner password
pdfcrypt encrypt in.pdf out.pdf “” user_pwd 11100000 128 //18 bits encrypt with user password
pdfcrypt decrypt in.pdf out.pdf owner_pwd
if the owner password is empty, please use it in this way,
pdfcrypt decrypt in.pdf out.pdf “”
It means if the pdf only encrypted with user password, you can easily remove the password without the password.
If you forget the owner password, you can try pdfcrack to get it and use PdfCrypt to remove the owner password