Make scanned lecture notes searchable for faster revision
First try selecting or searching the PDF text. If each page behaves like a photograph, OCR is needed. Rotate pages, remove blanks and test a short sample before processing a large scan.
Check OCR before studying from it
Compare dense text, headings, tables and formulas with the original. Names, dates, equations and low-contrast words need manual checking. Apply consistent headings, retain original page references and use the searchable copy for navigation—not as a replacement for the source.