Guides
Twelve short pieces on what a PDF actually stores, so the tools make sense before you use them.
What is a guide for?
A tool page tells you what a button does. A guide tells you what is happening to your document, which is usually the thing that decides whether the result is the one you wanted.
Each one answers four questions in plain terms and then points at the tools for the job. These are the only pages on this site that scroll: everything else is an instrument, and an instrument that scrolls is a website with a widget on it.
The twelve guides
- How to make a PDF smallerWhere the bytes in a large PDF actually are, and which setting returns them.
- What DPI and quality actually changeResolution and encoder quality are two different dials. What each one does to a page.
- How page ranges workThe 1-3,7,10- notation, what counts as page one, and what happens to the pages you leave out.
- Merging PDFs and what happens to bookmarksWhat survives when documents are combined: outlines, links, form fields and file size.
- Removing a password from a PDF you ownOwner password or user password, what encryption actually protects, and what to do when you have neither.
- Redaction that actually removes the textWhy drawing over text does not remove it, and what a real redaction has to delete.
- What OCR can and cannot readWhich scans recognition reads well, which it does not, and what a text layer changes about a document.
- Why editing text in a PDF is limitedWhy a PDF is not a word processor document, what editing can do, and when to go back to the source.
- PDF forms, and why some cannot be filledReal form fields versus a scan that looks like a form, and what happens when you flatten one.
- Electronic signatures and digital signaturesA drawn signature and a certificate signature do different jobs. Which one a document needs.
- PDF/A and keeping documents readableWhat PDF/A actually requires, why it exists, and what this suite does and does not do about it.
- Are online PDF tools safe?What happens to a document you upload, what a local tool does instead, and how to tell which you are using.