PDF Utilities & Metadata

PDF utility tools online free — compare text content between PDFs, edit metadata (title/author/subject), compute SHA-256 hash, view detailed file information. Also: PDF Editor | Security | Compress | OCR.
Text Diff: Extracts text from both PDFs, then compares line-by-line. Green lines are added in PDF B, red lines are removed from PDF A. Text extraction quality depends on the PDF's internal structure. Scanned/image PDFs may not yield text.
Metadata: Reads and edits PDF document properties (title, author, subject, keywords, creator, producer). Changes are written to the PDF's document information dictionary. Standard PDF viewers display this metadata in File Properties.
Hash: Computes a cryptographic hash of the PDF file using Web Crypto API (SHA-1, SHA-256, SHA-384, SHA-512) or a fallback for MD5. Use for integrity verification or to check if two files are identical.
Info: Reads PDF document properties including page count, page sizes, metadata, font names, embedded file count, and encryption status.

What a PDF looks like inside

Every PDF is, at heart, a list of numbered objects. A page is not stored as one block of formatted text — instead, the file contains a page tree (a catalog that lists every page), and each page points to a content stream: a compact program of drawing instructions such as "place this glyph here, draw this line there". Fonts and images live in separate objects that pages share by reference.

At the end of the file sits the xref (cross-reference) table, which records the byte offset of every object. This is what lets a PDF viewer jump straight to page 300 without parsing the first 299 pages — and it is why deleting or adding pages requires care: the offsets must stay consistent.

Why this matters for the tools above: the Metadata editor writes the document information dictionary; the Info viewer reads the page tree, fonts and resources; and tools like Compress and Edit reorganize these objects (PDF 1.5+ can pack many small objects into compressed object streams, which is where most "compress PDF" savings come from). Export tools walk the content streams to pull text and coordinates back out.