Why Converting Traditional to Simplified Chinese in PDFs Requires a Combined Approach

A team working on a Hong Kong stock interim report discovered that batch-converting traditional Chinese characters to simplified in PDF format is far more complex than a simple find-and-replace operation. PDFs store text across multiple structural layers — including content streams, embedded fonts, and Unicode mappings — making any character-level change prone to cascading errors. The developers tested three distinct technical approaches, each with its own strengths and limitations, finding that none worked reliably on its own. Their primary method used redaction paired with PyMuPDF's high-level TextWriter API to delete original glyphs and insert new ones, offering strong verification but producing scrambled copy-paste text order. Ultimately, the team converged on a hybrid strategy combining case-specific handling with unified verification to balance visual accuracy, text-layer integrity, and practical reliability.