A scanned manual can look perfectly readable on screen while returning no search results. Its PDF may contain only pictures of pages. Optical character recognition, usually called OCR, can add a text layer that supports searching, copying, and further processing. That layer is useful, but it is not a verified transcription. Product codes, faded originals, and unusual typefaces need particular attention because a plausible-looking result can still contain the wrong characters.
Start with a usable scan
First check whether text is already present. Search for an unusual word and try selecting a sentence. Some PDFs combine text-based pages with image-only pages, so test several locations. One successful search does not establish that the entire document is searchable.
When making a new scan, keep pages straight, lighting even, and margins complete. Shadows along a book's spine and cropped characters are not defects OCR can reliably repair. If an important line is unreadable in the image itself, capture that page again. Increasing the file size of the same blurred picture will not necessarily improve recognition.
Choose settings for the material
Choose the document's language and the page range to recognize. A tool may support multiple recognition languages for mixed material. Inspect the available options instead of assuming that the interface language also matches the scanned text.
Save the result as a new file. For a searchable archive, an output that retains the page image and adds recognized text is often appropriate. Producing a fully editable document is a different task: columns, tables, and line breaks may be reconstructed incorrectly and need a separate layout review.
If the source contains private information, establish whether it may be processed by an online service before uploading it. A program that works locally and a web service receiving the file create different data flows. The easiest available button is not necessarily the appropriate route for internal documents.
Check important characters against the image
Search for several terms from different pages, including one near the end. Copy a short paragraph into a text editor and compare it with the scan. Pay attention to hyphens, accented characters, zero versus the letter O, and one versus similar-looking letters.
In a replacement-parts list, accurate item codes matter more than flawless surrounding prose. Check critical fields in full or clearly label the file as an unchecked OCR version. A searchable layer also does not automatically make a scan accessible: reading order, headings, and table structure may still be missing. Retain the original capture so that uncertain passages can be checked against their source later.