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LouiseMSEI
LouiseMSEI
Participant
February 8, 2021
Answered

Another PDF app was able to unlock PDF doc protected by password. Why?

  • February 8, 2021
  • 3 replies
  • 1300 views

Hello,

I just realised that another PDF program can unlock a protected PDF.

The PDF document had a password preventing modifications, except printing.

Can you explain why the document was not really protected ?

Is there a way to make sure this cannot happen?

Thank you !

 

Louise

This topic has been closed for replies.
Correct answer Dov Isaacs

To be a bit clearer about this.

 

The only password that provides strong protection is the password that you can set for opening the PDF file. That password is used to encrypt the PDF file such that if you don't have the password, a program reading the PDF file that doesn't have that password from the user cannot access the contenst of the file at all.

 

The ability to change the protections for modifications, printing, copying, etc. are controlled by a password, but that protection is only as good as the applications processing the PDF file. Adobe's PDF applications including Reader and Acrobat do obey those restrictions and won't let you change them without knowing the password. Regrettably, there are other applications that simply ignore the restrictions.

 

PDF is an ISO standard, not an Adobe standard and as such, we cannot control what mischief other vendors cause.

 

3 replies

Dov Isaacs
Dov IsaacsCorrect answer
Legend
February 8, 2021

To be a bit clearer about this.

 

The only password that provides strong protection is the password that you can set for opening the PDF file. That password is used to encrypt the PDF file such that if you don't have the password, a program reading the PDF file that doesn't have that password from the user cannot access the contenst of the file at all.

 

The ability to change the protections for modifications, printing, copying, etc. are controlled by a password, but that protection is only as good as the applications processing the PDF file. Adobe's PDF applications including Reader and Acrobat do obey those restrictions and won't let you change them without knowing the password. Regrettably, there are other applications that simply ignore the restrictions.

 

PDF is an ISO standard, not an Adobe standard and as such, we cannot control what mischief other vendors cause.

 

- Dov Isaacs, former Adobe Principal Scientist (April 30, 1990 - May 30, 2021)
    Dave__M
    Community Expert
    Dave__MCommunity Expert
    Community Expert
    February 8, 2021

    Thanks Dov!  I've had to answer questions regarding this very issue in the classroom for years.  

    My best,

    Dave

    Dave__M
    Community Expert
    Dave__MCommunity Expert
    Community Expert
    February 8, 2021

    This has been an issue for years... and it's not anything Adobe can control when it comes to the behavior of a piece of software that is not produced by Adobe (as I understand it).  Many companies produce applications that open, view and manipulate PDFs.  How and whether the engineers honor the security parameters is their call, unfortunately.

     

    My best,

    Dave

      T
      Test Screen Name
      Legend
      February 8, 2021

      Many apps ignore editing password. It's a useful hint but no protection. Acrobat should have warned you of this but many people ignore the warning. 

        LouiseMSEI
        LouiseMSEIAuthor
        Participant
        February 8, 2021

        Thank you Test Screen Name. So, in other words, Acrobat doesn't really protect my documents even if I put in a password against modifications?

        Is there another way to protect my documents? I want them to be opened, printed but not modified.

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