Cover vs the best local Ai engines
Leaking private PDFs (or client files) to an online Ai is bad. Luckily, offline Ai models can run locally without sharing your private info with the Internet. But they're much dumber. We wanted to know how well the best local Ai engines can handle redacting PDFs. So we launched a bake-off competition: Cover vs local Ai engines. See what we're learning with each bake-off competition below.
Local LLM Ai over-redacts. Cover auto-redacts properly & offers 1-click redaction edits.
When a local Ai buries your PDFs in over-redactions, you're stuck. There's no quick way to correct its errors. Cover is the opposite: Hold ⌥ Option and drag across any redactions you want removed.
The full bake-off data proof
Cover's automatic engine is fast and clean. And its edit tool allows you to quickly touch up anything missed.
Adobe Acrobat and Preview don't have a smart redaction engine to do 80% of the work for you. And local LLM Ai engines don't have a way to touch up the mess they make over-redacting regular words in your PDF. Imagine removing 78 extra redactions by Gemma, the best performing LLM!
| Engine | Personal info caught | Wrongly hidden | Median time / PDF |
|---|---|---|---|
| Cover | 100% | 12 | 3.2s |
| Gemma 4 12B Google | 93% | 157 | 26s |
| Phi-4 Microsoft | 75% | 149 | 37s |
| Qwen 3 Alibaba | 75% | 188 | 4.5m |
| Qwen 2.5 Alibaba | 65% | 167 | 23s |
| DeepSeek R1 14B DeepSeek | 63% | 122 | 4.1m |
| Llama 3.1 Meta | 67% | 260 | 24s |
| Apple on-device Apple | 50% | 129 | 4.6s |
| Gemma 3 Google | 69% | 623 | 24s |
| Privacy Filter OpenAI | 63% | 709 | 13s |
| Rampart America.gov | 36% | 370 | 0.1s |
| Privacy Filter Nemotron OpenMed | 41% | 1290 | 4.4s |
| Cover | Preview | Acrobat Pro | |
|---|---|---|---|
| Finds personal info on its own | ✓ | ✗ | Partial |
| Zero setup, no checkboxes | ✓ | N/A | ✗ |
| Works without the internet | ✓ | ✓ | Partial |
| Click a word to redact it | ✓ | ✗ | ✗ |
| Click a redaction to remove it | ✓ | ✗ | ✗ |
| Remove a whole group of redactions at once | ✓ | ✗ | ✗ |
| Un-redact whole pages at once | ✓ | ✗ | ✗ |
| Works on scans and photos | ✓ | ✗ | ✓ |
| Handles a whole folder | ✓ | ✗ | ✓ |
| Output still usable when shared | ✓ | ✓ | ✓ |
| Verifies removed info is really gone before saving | ✓ | ✗ | ✗ |
| Redaction certificate & log with every save | ✓ | ✗ | ✗ |
| Price | $99/yr | Free | $239.88/yr |
Preview and Acrobat never read the document for you. Everything they hide, you found by hand. And neither one checks its own work: Cover re-reads the finished file and confirms the removed text is actually gone, byte by byte, or it refuses to save. Every row here is in every Cover plan.
Last updated October 3, 2026 · Cover v1.0.2. Every engine redacted the same 18 real-world documents, 113 pages. Real PDFs, scored against a gold standard. Cover has the best automatic engine in the field, doesn't leave you with a mess of 157+ over-redactions to clean up and is blisteringly fast.