pdfium and pypdf return different text from the same PDF — four mismatches to know before you feed PDFs to an LLM

I assumed that "extract the text from this PDF" gives you the same characters no matter which library you use. It does not. Feed the same PDF to pdfium and to pypdf, and you get characters that only one of them returns, and characters that one of them silently replaces with a different sentence. Worse, neither output necessarily matches what a human sees on screen. The page says Hello world; the extracted text says something else. The page shows nothing; the extracted text has an extra line. Al