Scans your PDF's headings by font size and builds a clickable outline panel automatically. Review and edit the list before saving — free, in your browser.
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Long PDFs — reports, theses, manuals, eBooks — are much easier to navigate with a bookmarks panel: the sidebar outline every PDF reader supports, letting readers click straight to a section instead of scrolling. Adobe Acrobat lets you add these one at a time by hand. This tool reads your document's font sizes to find likely headings automatically, then lets you check the results before anything is saved.
How detection works: the tool measures the font size of every line of text using pdf.js, finds the most common size (your body text), and flags noticeably larger lines as heading candidates. Distinct font sizes are grouped into heading levels — the largest becomes H1, the next distinct size H2, and so on. Text that repeats on most pages at the same position, like a running header or footer, is filtered out automatically so it doesn't clutter the outline.
Detection is a starting point, not the final word — you can uncheck anything that isn't really a heading, fix a heading's level, edit its title, or add ones the scan missed before saving. The PDF's actual content is never touched; only a navigation outline is added.
Once you're done, you might also want to add page numbers, fix page orientation, or compress the file for email.