Tiny Online Tools
Correcting what nobody can see
A scanned PDF that has been through OCR carries the scan as an image and the recognised words as invisible text sitting on top of it. When the recogniser gets a word wrong, the picture still looks perfect — it is only search, copy-paste and screen readers that quietly fail.
This tool edits that hidden layer. The scan is not re-encoded, re-compressed or re-drawn.
How the file is changed
The page's content stream is a list of operators: some draw the scanned image, some position and show text. The stream is lexed, and only the string operand of an invisible text operator is replaced. Every other byte's meaning is preserved — the positioning operators, the graphics state, and the operator that paints the scan all pass through untouched.
That is why the corrected page cannot shift, blur or recompress. It is not a promise; it is a consequence of not regenerating anything.
Verification you can read
After writing, the result is re-opened and three checks run on every changed page:
- Text — the corrected words are what a text extractor now returns.
- Invisibility — the layer is still drawn in render mode 3, and the count of visible glyphs is unchanged.
- Pixels — the corrected page is rendered and compared against the original render, pixel by pixel. The changed ratio should be zero.
All three results are shown before you download, pass or fail.
When it refuses
Some pages cannot be rewritten safely: a content stream using a filter that cannot be decoded, or a text block that mixes visible and invisible glyphs so the visible ones cannot be guaranteed intact. Those pages are refused by name and left exactly as they were. A refusal is the right answer — a silently corrupted file is not.
Characters the PDF's fonts cannot express are handled the same way: where possible a standard Helvetica is embedded to carry the replacement, and where that is not enough, the edit is skipped and named.
Privacy
Parsing, editing, saving and verification all happen in your browser. The PDF is never uploaded.