docmask.app DocMask runs entirely on your computer — your file never reaches a server, never appears in an AI training set, never needs an IT-team SaaS approval. It swaps personal data in Word, Excel and PDF (plus legacy .doc / .xls) with reversible aliases before you paste them into ChatGPT, Claude or Copilot. Review every change in a side-by-side preview, keep the mapping encrypted on disk, then one-click restore the AI's answer back to the real values.