Start with the representation
A PDF can contain selectable text, scanned images, or both. OCR adds recognized text to images; extraction reads available text into another form. Either stage can introduce errors. The original remains necessary for checking what the page actually shows.
Keep three layers: original files; working derivatives such as OCR PDFs or extracted text; and a manifest connecting them. Assign stable document IDs before changing filenames. A derivative's nicer title should not break references to its original.
Inspect a representative sample
Check a clean text page, a scan, a table, a footer, and a page with handwriting or unusual layout. Copy a passage into plain text and compare its reading order and characters. Pay particular attention to negatives, decimal points, names, dates, and column alignment.
A table can extract all its words yet lose which value belongs to which row. Treat “text present” and “structure preserved” as separate checks. If the task concerns a table, inspect cells and headings directly.
A cautious OCR exercise
For an unsigned, image-only practice PDF, after installing OCRmyPDF and its dependencies using the official installation guide, a basic command is:
ocrmypdf --deskew --rotate-pages input-scan.pdf output-searchable.pdfUse a new output filename and inspect the result. OCRmyPDF documents these options and warns that image processing can affect content. Its text sidecar can omit pages that already contained text, so do not assume that sidecar alone contains the entire document. [source]
Do not experiment on an operative signed original. Keep originals unchanged and confirm the appropriate process before making derivatives of signed material.
Record coverage and errors
| Field | Purpose |
|---|---|
| Document ID and original path | Preserve identity |
| Page count and version | Detect missing or changed material |
| Derivative path | Locate the processed copy |
| Extraction method | Explain how text was produced |
| Problem pages | Keep failures visible |
| Review status | Distinguish produced from checked |
A blank extracted page should remain in the manifest. Do not drop it and report a smaller record as complete. For email, preserve attachments and relationships to the parent message.
Try it: an OCR inversion
The image says “Payment was not approved.” Extracted text says “Payment was now approved.” What should the analysis do?
Check your understanding
Flag the extraction error and use the original image to verify the statement. Correct the working text with a record of the correction, or supply the verified passage separately. Then identify outputs that may depend on the erroneous text. A better prompt cannot reliably restore a missing negative that the model never received.
Know when to stop cleaning
If successive transformations reduce legibility or erase content, return to the original and choose a different method. The goal is a faithful, traceable representation, not an attractive text file at any cost. Keep an exception queue for material requiring manual review.