pdfio

By design, PDFio does not handle PDF rendering or viewing, requiring additional libraries for display purposes, which complicates projects needing visual output, as admitted in the README.

As a C library, it requires manual memory management and lower-level programming, posing a barrier for developers accustomed to higher-level languages with more abstraction.

Focuses on low-level access, so common tasks like form filling or annotation editing may require more code compared to libraries with higher-level APIs, increasing development time.

Documentation is split into multiple files (e.g., INSTALL.md, CHANGES.md), which can make it harder to find comprehensive information quickly, as noted in the README's instruction to read documentation first.