Technical Summary: PDF (Portable Document Format) is an ISO 32000 standard maintained for device-independent document presentation across operating systems.
The Core PDF File Structure
A valid PDF document consists of four main sections: Header, Body (containing pages, text objects, and fonts), Cross-Reference Table (XRef), and Trailer.
PDF/A vs PDF/X Standards
PDF/A is designed for long-term digital archiving by prohibiting dynamic features like JavaScript and external font references.