Redacting sensitive information within PDF files

[Chrius56000]

. . .Can I advise all Members who upload documents here for Expert Members to advise on, that Adobe PDF is NOT a secure method of redacting sensitive information – I have downloaded several examples from this Section of the Forum that "appear" to have been adequately blanked out, but the latest version of Adobe Acrobat Reader for Android with all its stupid "Generative Summary" A.I. rubbish completely deleted the black scribblings–out and all the OP's personal information was revealed in full simply with a tap on the "Generative Summary" bit!

. . .Also, please do NOT use the Adobe Acrobat Reader tools on Android or elsewhere to "redact" the sensitive information – this simply adds the "redacting" as an additional layer that can be easily removed, or, if the document is opened in Word, Libre Office, etc., the "redacting" simply won't appear – I got a Technical Circuit Diagram sent to me that had been "redacted" this way, and all the detailed technical info the uploader wanted to hide became visible as soon as I opened it in Word!

. . .The best way to ensure that such information is rendered truly unreadable is to scan the document into a PC as an image and then use a "clone brush" or "eraser brush" tool to "paste" the white background pixels over the personal info, and then "flatten" the layers before converting to PDF again – I know this works because a Parking Company did this to me when I wanted Landowner Contact Details to try and get one of their scamming "invoices" cancelled, and it was totally impossible to retrieve the redacted info from a document prepared this way!

 

[yorkie]

. . .Can I advise all Members who upload documents here for Expert Members to advise on, that Adobe PDF is NOT a secure method of redacting sensitive information...

I think you mean that certain redaction tools within the software won't fully redact the information.

. . .The best way to ensure that such information is rendered truly unreadable is to scan the document into a PC as an image and then use a "clone brush" or "eraser brush" tool to "paste" the white background pixels over the personal info, and then "flatten" the layers before converting to PDF again – I know this works because a Parking Company did this to me when I wanted Landowner Contact Details to try and get one of their scamming "invoices" cancelled, and it was totally impossible to retrieve the redacted info from a document prepared this way!

There are various tools that will fully redact information, but yes, this method would certainly work, among others.

 

[Merseysider]

On a mobile, this can also be achieved by covering over the sensitive info once in white, then once in black, then screenshotting.

Drawing over it only once leaves it potentially visible simply by shifting the contrast up/down.

 

[Haywain]

Isn't it better to post letters or whatever as an image rather than a pdf anyway? I certainly find it easier to look at the content of an image rather than download a pdf.

 

[125Spotter]

About 10 years ago, I had a battle with my then local council over how they redacted 'personal information' on their planning portal: telephone numbers, email addresses, signatures etc. in submitted letters. They were doing exactly as you suggest by drawing black boxes without a layer merge or removal of the text, which made the information trivially retrievable. I found it when my email address appeared in a search engine result, despite the alleged (to the naked eye) redaction.

They did change their redaction method as a consequence, but also responded along the lines that "technology moves on and it is now possible to copy/paste information out of documents", which gave me a chuckle – I was tempted to retort that clipboards have been around since the near beginning of the digital age, and it was simply a foolhardy redaction methodology, but it would have fallen on deaf ears.

Can I advise all Members who upload documents here for Expert Members to advise on, that Adobe PDF is NOT a secure method of redacting sensitive information

PDFs can be securely redacted, but it's important that it's done correctly. That means merging layers (as opposed to simply drawing black boxes over the top of text) or removing the actual text if this is embedded in the document (as opposed to the PDF being a photograph/bitmap where the inline text is not present as a vector and has not been OCRed). The latter may not be achieved even with a black rectangle+layer merge tool which influences the rendering of the final document, but does not remove the underlying text component from the document.

Perhaps better advice here would be that PDFs should be avoided unless you are sure your redaction method is correct. The simplest methods are often the best and easiest for people to be assured by – people often add pieces of paper over a physical copy of their document and take a photograph, which leaves no room for concern as to whether any information remains.

 

[John R]

I think this is a very important point, and maybe the pinned thread that makes mention for those seeking advice to redact documents should be amended to link to a simplified version of the above to alert posters to the risk.

 

[yorkie]

Isn't it better to post letters or whatever as an image rather than a pdf anyway? I certainly find it easier to look at the content of an image rather than download a pdf.

Potentially yes, though in my experience, most browsers these days will show a PDF seamlessly.

 

[jumble]

. . .Can I advise all Members who upload documents here for Expert Members to advise on, that Adobe PDF is NOT a secure method of redacting sensitive information – I have downloaded several examples from this Section of the Forum that "appear" to have been adequately blanked out, but the latest version of Adobe Acrobat Reader for Android with all its stupid "Generative Summary" A.I. rubbish completely deleted the black scribblings–out and all the OP's personal information was revealed in full simply with a tap on the "Generative Summary" bit!

. . .Also, please do NOT use the Adobe Acrobat Reader tools on Android or elsewhere to "redact" the sensitive information – this simply adds the "redacting" as an additional layer that can be easily removed, or, if the document is opened in Word, Libre Office, etc., the "redacting" simply won't appear – I got a Technical Circuit Diagram sent to me that had been "redacted" this way, and all the detailed technical info the uploader wanted to hide became visible as soon as I opened it in Word!

. . .The best way to ensure that such information is rendered truly unreadable is to scan the document into a PC as an image and then use a "clone brush" or "eraser brush" tool to "paste" the white background pixels over the personal info, and then "flatten" the layers before converting to PDF again – I know this works because a Parking Company did this to me when I wanted Landowner Contact Details to try and get one of their scamming "invoices" cancelled, and it was totally impossible to retrieve the redacted info from a document prepared this way!

Related but different people should also be mindful that Word documents can contain the authors details in its properties

 

[Railguy1]

For physical copies I normally take a picture (or scan of the document using Microsoft Lens or similar apps). Then open the image in MS paint. You can email the image to yourself if you need a quick way to transfer the file from phone to laptop.

For digital only copies I press the print screen button on the keyboard, then open MS paint then press copy (CTRL then C keys).

Once the above is achieved I use the rubber tool or paint brush to remove/alter the sensitive data. I then save the image under a different file name.

 

[BingMan]

. . .Can I advise all Members who upload documents here for Expert Members to advise on, that Adobe PDF is NOT a secure method of redacting sensitive information – I have downloaded several examples from this Section of the Forum that "appear" to have been adequately blanked out, but the latest version of Adobe Acrobat Reader for Android with all its stupid "Generative Summary" A.I. rubbish completely deleted the black scribblings–out and all the OP's personal information was revealed in full simply with a tap on the "Generative Summary" bit!

. . .Also, please do NOT use the Adobe Acrobat Reader tools on Android or elsewhere to "redact" the sensitive information – this simply adds the "redacting" as an additional layer that can be easily removed, or, if the document is opened in Word, Libre Office, etc., the "redacting" simply won't appear – I got a Technical Circuit Diagram sent to me that had been "redacted" this way, and all the detailed technical info the uploader wanted to hide became visible as soon as I opened it in Word!

. . .The best way to ensure that such information is rendered truly unreadable is to scan the document into a PC as an image and then use a "clone brush" or "eraser brush" tool to "paste" the white background pixels over the personal info, and then "flatten" the layers before converting to PDF again – I know this works because a Parking Company did this to me when I wanted Landowner Contact Details to try and get one of their scamming "invoices" cancelled, and it was totally impossible to retrieve the redacted info from a document prepared this way!

Print the document; then redact the sensitive information with a permanent marker or a pair of scissors; then scan the redacted document.
Same as when you are asked to sign a PDF