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Topic: PDF to DXF Conversion - Security? Post Reply Post New Topic
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Steveboyy
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Quote Steveboyy Replybullet Topic: PDF to DXF Conversion - Security?
    Posted: 27 Feb 12 at 4:45PM
I recently purchased your Pro version so I can apply security to my CAD drawings. However, my CAD program can convert a PDF back into a DXF drawing file even when security protocols are applied to the PDF.

How is this possible? Can you do something to fix this in the next version as it defeats the purpose of PDF in the first place - I may as well just send the DWG file.

Note: I stop at not applying a security unlock to viewing the drawing as my client needs to be able to open it.

Steve.
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PapiBourgenot
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Quote PapiBourgenot Replybullet Posted: 27 Feb 12 at 6:35PM
Hi Steve,

   Can you confirm which encryption you are using? This is located in Preferences >> Security >> Encryption Level >> etc.

   I would recommend that you use "128 bit AES" as the most secure. Can you confirm that you can still import the data with that setting?

   Finally, please keep in mind that when you lock a PDF, you are preventing the end-user from modifying, (or other limitations) the PDF itself. However, it is still possible to view the PDF, and some access to the content is still made available. To make it foolproof to prevent importing (if the above does not work), your best bet will be to print to the PDF format as an "image" rather than an object-based PDF, or to use an alternate object based format. For example, you may find that your CAD program might be able to export to an EMF, or WMF, and those formats, once converted to PDF, may not be "importable".

   I hope that helps.

   Kindest regards,

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Steveboyy
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Quote Steveboyy Replybullet Posted: 27 Feb 12 at 7:01PM
Thanks for you help Papi.

I wasn't actually locking the file, just applying preventions for changes, etc; so I now tried doing as you suggested by locking the pdf with a password and 128 AES and guess what - I can still convert it to a DXF file.

Only by taking the next step of encrypting it, will it then finally prevent conversion to DXF.

I don't know how my CAD program is doing this, but this is a big security problem as I deal with other engineers (as clients) and reverse engineering my drawings cannot be allowed to happen.

Steve.
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Michel_K17
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Quote Michel_K17 Replybullet Posted: 27 Feb 12 at 9:43PM
Hi there Steve,

   Here is the explanation (from the Adobe PDF specification):

   "Once the document has been opened and decrypted successfully, the application has access to the entire contents of the document. There is nothing inherent in PDF encryption that enforces the document permissions specified in the encryption dictionary. It is up to the implementors of PDF consumer applications to respect the intent of the document creator by restricting user access to an encrypted PDF file according to the permissions contained in the file."

   Or put another way, once your CAD program has been given access to the file, it can do whatever it wants with the data. Technically, they should not if they were to honor the switches to lock the PDF, but compliance is up to them.

   I would definitely go ahead, and either:
  1. encrypt the PDF (and share the password) since that seems to work,
  2. or distribute the PDF as an image,
  3. or try "re-printing" as explained below.

   Here is an alternative that might work. This is called "re-printing":
  • Create the PDF like you normally would via PDF reDirect Pro.
  • Click once on the output PDF file so that it appears in the Preview area (lower RHS).
  • Click the small printer icon in the Preview header.
  • Select the PDF reDirect Pro printer.
  • A second output PDF will appear in the Merge List.
  • Delete the first output PDF.
  • Save the remaining PDF to a final destination.
  • Check to see if you can import that PDF in your CAD program.
    Cheers!

Michel Korwin-Szymanowski
EXP Systems LLC
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Steveboyy
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Quote Steveboyy Replybullet Posted: 27 Feb 12 at 10:12PM
Well Michel, I tried as you suggested with re-printing, but I can still import the PDF and convert to DXF.

I don't know how the CAD program is opening or unlocking it.

I am not sure how to distribute the PDF as an image, but that sounds like the file size will grow, which is undesirable as I merge lots of drawings.

Does this mean that any other PDF writer would give the same result? IE, say Adobe, or is it peculiar to your program only? Don't get me wrong, I have used your free version for years and love it, but upgrading to the pro version was supposed to stop this "reverse engineering" from happening and it has not been entirely successful.

Of course, I may have a very clever CAD program that others may not have, but it is still baffling how it can do this. I have even tried it on locked Word documents and it will convert those to DXF too.

Steve 
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Michel_K17
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Quote Michel_K17 Replybullet Posted: 27 Feb 12 at 10:23PM
Hi Steve,

   OK, thanks for trying. And yes, the image format could make for much larger files.

   Yes, most PDF writers will experience the same problem as many use the same PDF conversion engine (Ghostscript). You could try alternate PDF writers that use proprietary engines such as Adobe Acrobat or BlackIce [here].

   Otherwise, is password encrypting a possibility for you?

   Best regards,

Michel Korwin-Szymanowski
EXP Systems LLC
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Steveboyy
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Quote Steveboyy Replybullet Posted: 27 Feb 12 at 11:41PM
Thanks for your prompt replies Michel.

Password protection is not really an option as it adds a "nuisance"
layer to our customer support.

I have tried downloading a trial version of Adobe Writer X (it's the only one available for trial on their site), but their UI is giving me trouble in logging in to enter my details. So no go.

Is Black Ice a compete PDF writer like yours? I notice there is a demo on their site but there are so many products that it is confusing.

Is there any chance that you would address this in a later version are are you locked into using Ghostscript?

Steve


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Steveboyy
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Quote Steveboyy Replybullet Posted: 28 Feb 12 at 5:28PM
I have been using your free version now for years Michel, and now the Pro version, as I really like its simplicity and I will be staying with you.

I trialled Nitro Pro, but had the sample security issues and I hated the UI. Yours is so much nicer and easier to use.

PDF reDirect is an excellent program, especially with your fantastic support.

I think the secure PDF to DXF is just a quirky thing and hopefully a little known work around.

Keep up the good work.

Steve.

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Michel_K17
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Quote Michel_K17 Replybullet Posted: 28 Feb 12 at 10:34PM
Thanks Steve: I appreciate your kind words. Smile

Cheers!

Michel Korwin-Szymanowski
EXP Systems LLC
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Michel_K17
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Quote Michel_K17 Replybullet Posted: 28 Feb 12 at 10:42PM
And to answer your other question: I am not "locked in" into using Ghostscript (in fact, the current version of PDF reDirect will also support the Adobe "Distiller" engine - which is not free).

But I am considering changing to a commercial solution if I find one that works well.

Thanks again,

Michel Korwin-Szymanowski
EXP Systems LLC
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