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I wish to take a PDF or Word document and run stripes through the text to obscure it so that complete confidential information is not revealed, but one could compare against an unstripped other file to detect whether the unstripped version was a copy of the original file in at least some parts.

How can such stripes be added? I searched Google and couldn't find anything using the terms like stripe pdf tool obfuscator. I created a zebra stripped PNG file like this:
stripes
But using it as the watermark in Microsoft Word 2011 without any washout gives grey strips that reveal the text underneath. Exporting to PDF does show in Adobe as black stripes, however, the text under the black stripes remains and can still be copied, for security, I'd like to convert the file to an image based PDF and not contain any text under the black stripes. I tried exporting images from PDF, but that only gave me the zebra stripping, no image of the text. I don't want to just print it all out and scan it back in again due to the document being 1,500 pages long, and so do not want to waste the paper, nor deal with scanning that many pages.


Taking the PDF exported from Word with Zebra stripes, I can select a single character under the zebra stripes on each page of the document for redaction, once I've touched every page, I can then apply the redaction and remove hidden information to convert each page to an image of the page, no text remaining.

While this works, it requires each page to be touched to redact at least a character on each page in order for Adobe to convert that page to an image.

Is there an easier way to tell Adobe to convert each page to an image of the page without having to touch every single page?

  • Have you tried using a PDF printer instead of saving or exporting as PDF? – fixer1234 Mar 19 '16 at 8:06
  • @fixer1234 I tried that and got the same results and same file size. In word, the print dialog has special PDF handling that appears to result in the same code path as save as PDF. – WilliamKF Mar 19 '16 at 15:28
  • I don't really understand what the point is. These stripes won't really obscure the content, not even visually. What's the goal here? – Daniel B Mar 19 '16 at 15:34
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Even if you add stripes on top of text in a PDF, the original text content is still present in the document and can still be revealed.

  • That's an important point. Acrobat Pro contains a redaction tool to help with that. – Daniel B Mar 19 '16 at 15:32
  • @DanielB I used the redaction tool, but it warns other tools may allow text to be copied and I saw this first hand, when viewed in dropbox, the text was copyable. – WilliamKF Mar 19 '16 at 15:42
  • @WilliamKF Then you didn’t use it correctly. The redaction tool physically removes completely covered characters from the file. That is after applying the redactions, of course. – Daniel B Mar 19 '16 at 15:49
  • @DanielB Correct, I used the secure document feature to prevent text from being copied etc. The redaction tool does not recognize the zebra stripes as being redacted text. The tool requires you manually mark text for redaction in the flow the text reads. That means each intersection of a line of text with zebra strip would have to be manually marked. Partial characters cannot be redacted that straddle a zebra line. Each page would take about 30 seconds per line, 60 lines per page, 1,500 pages, total 750 hours of labor. – WilliamKF Mar 19 '16 at 15:59
  • That's not true. You can also draw rectangles. Text will be removed where they overlap. However, instead of asking about the solution, ask about the problem. – Daniel B Mar 19 '16 at 17:27
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Here is how to do this efficiently:

  1. In Microsoft Word, add the zebra watermark as described in the original question.
  2. Save-as that word document to Adobe PDF format.
  3. In Adobe Acrobat Pro, File -> Export To -> Image -> PNG and to create a PNG file for every page of the document, uniquely named by their page number. Place the files into a new temporary folder to make later alphabetical selection of them all easier.
  4. In Adobe Acrobat Pro, File -> Create -> Combine Files into a Single PDF...
  5. From the resulting Combine Files dialog, select Add Files... menu item in upper left of dialog.
  6. In the choose file dialeg, navigate to the folder where the exported PNG images are located from step 3, ensure they are sorted alphabetically, and then select all the files to add in alphabetical order by first selecting the alphabetically first file and then (on a Mac) shift clicking the last one alphabetically, to select the whole range in alphabetical order. Press the Add files button to add the selected files.
  7. Double check the files are in the correct numerical order in the Combine Files dialog by page number in the title of each image.
  8. Click Combine Files button in the lower right of Combine Files dialog.
  9. Save the resulting PDF document.

You now have a PDF with zebra stripes and no text, just an image of text, so the characters under the stripes are not present anymore.

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The rather pedestrian but un-hackable method would be to print it, then scan the print.

  • Yes, considered that, but would rather not waste 1500 sheets of paper. – WilliamKF Mar 19 '16 at 15:29
  • Then your alternative is to export each page as a pure image file, jpg, tif, png etc... which will be colossal compared to the original file – Tetsujin Mar 19 '16 at 15:34
  • I tried that, but only the zebra stripes were exported by Acrobat, not the image of the text. – WilliamKF Mar 19 '16 at 15:41
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Another way you could do this is to create your word document, save it as a pdf, and then run it through free PDF Redactor. You would have to draw the marks you require, however, it would completely flatten the image to remove text and sanitize any information in the pdf.

Full disclaimer, I built this.

  • The OP discusses the document being 1500 pages. These kinds of free web services won't typically accept a document of more than a relatively small size. Do you know what its limits are? – fixer1234 Jan 31 at 8:01
  • It's limited to 100mb at the moment, but if the file is 1500 pages at 300dpi under the best circumstances you'd be looking at 300kb/page*1500 = 439mb which would then get recompressed, but the file size returned to the user would be quite large. I actually built this- if someone has a file that is 1500 pages and personally needs help, reach out to me via intercom on freepdfredactor.com and I will see what I can do for you. – levinology Jan 31 at 8:13

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