Those characters simply won't show up when the PDF is viewed because the PDF didn't contain any information about how to display them. Since redaction in the text layer works by performing simple text substitution in the text stream, you may create replacement text that contains characters that were not previously in the PDF. This has an unfortunate consequence for redaction in the text layer. So if a document doesn't contain a particular letter or symbol, information for rendering the letter or symbol is not stored in the PDF. Most PDFs are optimized to only embed the font information for characters that are actually used in the document. One of the PDF format's strengths is that it embeds font information so that documents can be displayed even if the fonts used to create the PDF aren't available when the PDF is viewed. It would take a lot more effort to write a redaction tool that scanned all possible places content can be hidden inside a PDF besides the places that this tool looks at, so please be aware that it is your responsibility to ensure that the PDFs you use this tool on only use the capabilities of the PDF format that this tool knows how to redact. There are so many exotic capabilities in PDF documents that it would be difficult to list them all, so this list is a very partial list. embedded files, multimedia, and scripts.Besides a document's text layer, metadata, and other components of a PDF document which this tool scans and can redact text from, there are many other components of PDF documents that this tool does not look at, such as: Of exotic capabilities used rarely or in specialized circumstances. The PDF format is an incredibly complex data standard that has hundreds, if not thousands, Limitations Not all content may be redacted The example.py script shows how to redact Social Security Numbers: python3 example.py document-redacted.pdf
However, you should use the pdf_redactor module as a library and pass in text filtering functions written in Python, since the command-line version of the tool does not yet actually do anything to the PDF. Pdf_redactor.py processes a PDF given on standard input and writes a new, redacted PDF to standard output: python3 pdf_redactor.py document-redacted.pdf Get this module and then install its dependencies with: pip3 install -r requirements.txt Rewrite, remove, or add XML metadata using functions that operate on the parsed XMP DOM (e.g.wipe out all metadata except for certain fields). Rewrite, remove, or add new metadata fields on a field-by-field basis (e.g.replace social security numbers with "XXX-XX-XXXX"). Use regular expressions to perform text substitution on the text layer (e.g.Graphical elements, images, and other embedded resources are not touched. the Document Information Dictionary, a.k.a.the text layer of the document's pages (content stream text).This Python module is a general tool to help you automatically redact text from PDFs. Pdf-redactor uses pdfrw under the hood to parse and write out the PDF. A general-purpose PDF text-layer redaction tool, in pure Python, by Joshua Tauberer and Antoine McGrath.
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