[Feature Request] Add secure PDF redaction to the document editor

Description Feature request It would be very useful to have a secure PDF redaction feature built directly into the Paperless-ngx document editor. A previous Feature Request for this functionality already exists: • #5967 – "Feature to censor pdf" That discussion was later closed due to lack of community support. I would like to bring the feature up again with a more specific use case. Use case Paperless-ngx is already the central place for storing and managing documents. In many cases, however, a document needs to be shared with another person while certain personal or confidential information must first be removed. For example: • a name • an address • a date of birth • an account number • other personal or confidential information Currently, this requires exporting the PDF from Paperless-ngx, opening it in a separate PDF application, performing the redaction there, and then using the resulting file for shari…