PDF Secure
Current time: 09-20-2018, 01:35 PM
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Author: mybest
Last Post: ynopum
Replies 5
Views 2437

[Problem] PDF Secure
#1
Dear member.
I have question to ask

1. How to remove "secure" of pdf? For example if I want to insert a page into my pdf file.

2. How to make my pdf file to became "real secure" so no one can edit?

Regards.
mybest
An Engineer must have a SIX sense
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#2
Use this program to remove the protection:
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There are 3 types of protection of PDF files:
1. Forbid editing (copy, print, etc.) - this can be very easily bypassed using the above program.
2. Use a password to open the file - this can be bypassed by the above program, but needs too much time. Also anybody who tries to open the PDF needs the password to do so. Then, having the password he can do almost everything with the PDF.
3. Use tricks. The variety of these is not big. Generally the idea is to make the data in the PDF difficult to be edited:
- decomposing the text letters to splines, or other graphics objects, so simple copying of the text will not work anymore.
- converting the graphics to a raster image.
- splitting the raster image to many small raster images.

Generally all these can be bypassed using OCR programs like Abby FineReader that convert raster images to some other usable format.

There should be also some option to make "improper" PDF file, that can be opened properly by Acrobat. I haven't seen yet such intentionally "damaged PDFs" that open with mistake.

Another question is if you need to show somebody that a file has been edited - this is called usually "signature". It gives information if the file was kept untouched, or not.
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#3
Thank you ynopum, It's the answer for question number 1. Is there any answer to question number 2? Is it possbile to make my pdf file "Real Secure"? I don't want someone use this application to delete protection of my file.
regards.
mybest.
An Engineer must have a SIX sense
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#4
As I can't imagine your specific case (type of the contents, what users will try to modify it, and what they may want to modify) I will suggest you the following easy way for raster conversion, that will prevent easy copying, and modifying especially of the text contents.

1. Make your PDF

2. Open it in Adobe Acrobat (the full one, not "reader' only)

3. Export the PDF to a raster images (File/Export/Image/PNG) giving a proper resolution, at least 300 dpi if you want the prints to look nice)

4. Close the file and create a new PDF using these exported images (there are several ways to reach this option in Adobe Acrobat).

This doesn't protect from printing!
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#5
I´m afraid that is not enough!
A good OCR program can restore "quasi" 100% of the contents...
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#6
If the data is "top-secret" somebody can make an .exe program that shows the pages (raster images would be the easiest way to be used in standalone executable), and the program can disable Printscreen button, also any known OCR applications that are loaded in the memory, etc.

Another option is to use a Flash application style, as this is very popular way to prevent the users from mass-copying documents on webpages. In this case the user's browser will be used to show the flash document.

It depends how "deep" is the problem with security. And regarding we are bounded to the PDF format there aren't many options to keep the document pleasantly readable for the human, and difficult to be recognized by OCR software.
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