How to protect PDF eBook from being opened without permission?

Question: I made a PDF from a Microsoft Word document. So far so good. Now what is the best way to protect my PDF eBook to ensure I don't get thousands of unauthorized copies of my PDF eBook floating around the internet? I don't want to use a simple password to protect the PDF document, because judging by the amount of unauthorized PDF copies of other eBooks I have seen available on the internet, that security method is very weak.

Answer: According to your needs, you can try to encrypt PDF by 128-bit password. VeryPDF Encrypt PDF has such function which allows you to protect PDF eBooks absolutely safe. There are many versions of this software available: GUI version, command line version, COM version. Here I will take the command line version for examples. In this article, I will take the command line version for examples.

Step 1. Download Encrypt PDF Command Line

  • When downloading finishes, there will be a zip file. You need to extract it to some folder then you can find the executable file in MS Dos Windows.
  • Open help.txt then you can find all the parameters and examples in it.

Step 2. Protect PDF eBooks by setting password.

Know a little bit more about password encryption level.

The process of encryption can help you hide data or the contents of a message in such a way that the original information can be recovered through a corresponding decryption process. For now there are two levels available: 40-bit and 128-bit Encryption. Compared to 40-bit encryption, 128-bit encryption offers 88 additional bits of key length. This translates to 288 or a whopping


additional combinations required for a brute-force crack. Based improvements of 128-bit Encryption, security experts expect that 128-bit encryption is very hard to be cracked.

  • When you use this software, please refer to the usage and examples in help documents.
  • Here are some usage and parameters for your reference. EncryptPDF [options]
    -u                 : user password.
    -w                 : owner password.
    -p                 : permission print.
    -c                 : permission copy.
    -m                 : permission modify.
    -n                 : enable adding and changing text notes and AcroForm fields.
    -e [128 or 40    ] : set encrypt level.
    -k                 : set for all permission bits.
    -v                 : view the PDF file after encrypt.
    -l [log file name] : specify log file for output message.
  • When you need to encrypt PDF eBooks, please refer to the following command line templates.
  • EncryptPDF -i c:\sample.pdf -o c:\out.pdf -w owner -u user -l c:\out.log
    By this command line, we can encrypt PDF file both open password and owner password and input log information.
    EncryptPDF -i c:\sample.pdf -w owner -u user -e 128 –p
    By this command line, we can encrypt PDF by 128 bit level password of both open password and owner password.
    EncryptPDF -i c:\sample.pdf -w owner -u user -e 40 -k –828

Normally speaking, if you set both of open password and owner password by 128-bit level password, encrypted PDF file can not be opened or cracked easily. During the using, if you have any question, please contact us as soon as possible.

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