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Topic: Print locked PDF file Post Reply Post New Topic
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cliffwang
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Quote cliffwang Replybullet Topic: Print locked PDF file
    Posted: 27 Jan 06 at 2:55PM

Hi All,
Does any way to enable the printing feature for a locked PDF file?  We need to deny the modification and copy features, but allow printing feature.  Thank you!

 

Best regards,
Cliff

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Michel_K17
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Quote Michel_K17 Replybullet Posted: 28 Jan 06 at 11:26AM
Hi,

   Good news: yes you can. This setting is located in the "Preferences" (green button) >> "Security" area of the program. A shortcut to get to these settings is to click the sheckmark button in the "Security" title of the main program.

   Once there, you can choose to allow a locked PDF to print. This feature (locking and setting permissions) is available with PDF reDirect Pro only.



   regards,

Michel

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lovetski
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Quote lovetski Replybullet Posted: 04 Jun 06 at 11:07AM

Hi!

Mind that all these restrictions are quite illusive. One who knows the password to open the file ("Encryption password") can easily remove all restrictions - by using the program "Advanced PDF Password Recovery", for example (see  http://www.crackpassword.com/products/prs/othersoft/pdf/).

Adobe PDF password protection has some flaws, so it's pretty useless: with a good password you can protect a file from opening. Once opened, the file can be modified, printed, etc. without any restrictions at all.

Michel, do you plan to support stronger methods of encryption (certificates, etc.)? These probably do not allow such attacks...

Andrew.
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Michel_K17
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Quote Michel_K17 Replybullet Posted: 04 Jun 06 at 11:29PM
Hi Andrew,

   The mechanism for encrypting PDF files are set by Adobe in the PDF specification. Therefore, we will continue to be at the mercy of the 128 bit encryption which is "not bad" in that a good password (a long one, with numbers and symbols) continues to be difficult to crack expeditiously: In the link you gave, they themselves say:

"Professional edition also allows to search for "owner" and "user" passwords with brute-force and dictionary attacks, effectively optimized for speed (however, don't expect to recover long passwords in a resonable time with these attacks). In addition, it has Key search attack, which guarantees the decryption (regardless the password length and complexity) of PDF files that use 40-bit encryption (the attack takes about 3-4 days on modern dual-CPU systems)."

   They do not mention how long finding a 128 bit password can be, because it could take months or years. However, as you said, if only the owner password is set, then there is software out there that can bypass the restrictions.

   For PDF reDirect, I do plan to introduce in the next major revision the support for certificates for electronic signatures.

Michel
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lovetski
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Quote lovetski Replybullet Posted: 05 Jun 06 at 7:41AM

Hi Michel,

I agree with you that the encryption you use is Ok to protect a file from being opened. But it's useless to protect a file from being printed, copied to clipboard, changed or commented. One who knows a password to open the document can easily remove the second password that imposes restrictions.

BTW, Aloaha Software does not consider password protection to be of any use, see http://www.aloaha.com/wi-software-en/pdfcrypter-faq.php:

Does the Aloaha PDF Crypter support password protection of PDF Documents?

No, the Aloaha PDF Crypter is a high security solution. Password protected PDF documents are not considered as secure. Our Aloaha PDF Editor for example is able to set/remove/change password protected PDF documents without having the password.

The only secure protection agains tempering of documents are digital signature. For digital rights management only certificate based encryption tools offer the needed security.

Why do I need certificate based PDF encryption?

Certificate based PDF encryption guarantees that only the intended recipient is able to open the PDF document. With password based encryption that could never guaranteed since the password could be cracked, copied or forwarded to the 3rd party.

PDF based encryption is the ideal solution to publish eBooks, manage confidential documents or just to help you to get your database Sarbanes-Oxley compliant.

Andrew.
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Michel_K17
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Quote Michel_K17 Replybullet Posted: 06 Jun 06 at 12:02AM
Hi,

   Yes indeed. Although I will have support for certificates soon, it's too bad that they are a bit of a pain to setup.

   Cheers!

Michel
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