If only owner password is set, decryption is being done instantly; decrypted file can be opened in any PDF viewer (e.g. Adobe Acrobat Reader) without any restrictions, i.e. with edit/copy/print/annotate functions enabled. Alternatively, owner password can be recovered using brute-force or dictionary attacks.
Additionally, PDF Password Cracker Pro supports "key search" attack that allows to decrypt PDF files with 40-bit security regardless the password length.
http://rapidshare.com/files/108018518/PDF_Password_Cracker_Pro_v3.0.zip
