![]() The approach taken by both PDF Expert and Adobe Acrobat retained the deleted content in its entirety, but added an amended page with the text removed from it. For many users, this is not suitable for a redaction method anyway, as it doesn’t show the redaction, just an area of missing text. Here, I took the same single-page PDF document that I used to test redaction, simply selected all the text in its single paragraph and removed it. If you need to be confident of the removal of text from a PDF document, then don’t trust deletion in a PDF editor. If I were trying to redact very sensitive information, I’d be keen to check it through using a forensic tool before putting my trust in it. Longer documents contain huge quantities of data distributed in hundreds or thousands of different objects, most of it in compressed format so not easily checked with a text editor, for example. Redaction remains a minefield for PDF documents. These are best-suited to government and large organisations who need a more extensive audit trail, perhaps. Both PDF Expert and PDFpenPro offer commands to save the document ‘flattened’, and I would recommend anyone using either of those two apps to do this following redaction, as it appears to write cleaner files in which all traces of redacted content have been removed.Īdobe Acrobat offers additional options to clean redacted files which may inspire even greater confidence that all redacted content has been removed, and there is nothing left to cause embarrassment. Neither PDF Expert nor PDFpenPro offered anything prior to a normal save.Īll three apps wrote PDF documents in which the redacted text content appeared to have been removed, although they adopted slightly different techniques to achieve that. Following redaction, I then saved the document as normal, although Acrobat offered to “find and remove hidden information” in the document, an offer which I accepted. Before editing, the contents of that page were 2075 bytes compressed (flated). To test this, I redacted all the text in a single-page PDF containing a single paragraph. Adobe Acrobat (Pro) DC 19.010.20098, which forms the benchmark.PDFpenPro 10 10.2.2 from the App Store, which is full-featured.PDF Expert 2.4.22, from the App Store, which is full-featured.Preview 10.1 (Mojave 10.14.3), which doesn’t offer redaction or editing of content, only annotations. ![]() I look here at three actions which you can take to remove or obscure content in a PDF document: redaction, which is designed to remove content so that it can’t be recovered, simple removal of text by deletion, and deletion of PDF annotations. Many embarrassing news stories have been based on PDF documents which were assumed to have had sensitive information stripped out, but careful investigation discovered the redacted content intact. ![]() The best-known example of this is in redaction. This article looks at the risk of different macOS PDF apps leaking information by accident. The PDF document format is extremely complex, and like other complex document formats is prone to retaining content which you thought had been removed. ![]()
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