Fix download with redaction for non-PDF files

Bug below described with a word file, but applies to any non-PDF format.

As a user with redaction rights

• Upload a Word file
• Redact file using NEV
• Download redacted version

=> the file downloaded is corrupted

Expected, for an "office" type of file (e.g., Word, text, PDF, etc)

• File is converted to PDF (only format to support redactions)
• File is downloaded with permanent redactions and can be opened normally