Adding to a PDF, not rewriting it
Most people looking for a PDF editor want one of two quite different things: putting something new onto a page, or changing the words that are already there. The first is what this tool does, and it does it well. The second is a different job that nothing on this site does, and it is worth knowing which one you are after before you start.
Which tool you need
Adding text, a note, a drawing or an arrow to a page
Edit PDF. Everything you add is written onto the page and stays where you put it, and a drawing is stored as lines rather than as a picture, so it stays sharp when the page is zoomed or printed.
Changing a word that is already printed in the document
Nothing here does that, and it is better to say so than to let you find out after twenty minutes. Retyping a PDF's own words means rebuilding its text and fonts, which is a different kind of tool. Ask for the document it was made from if you can.
Marking up passages for somebody to read
Edit PDF's highlight, underline and strike-through. They are written as real annotations, so the reader you send it to can select them, recolor them or take them off — which is what marking up means.
Hiding something private before you send the file
Do not use a box or a highlight for this. Nothing here removes what is underneath. Take the whole page out with Delete PDF pages, or redact it in software built for redaction.
Putting your name at the bottom of an agreement
Sign PDF is built for it, with a signature pad, a typed option and a date, and it can put the same mark on every page.
The same mark on every page, like a status or a logo
Watermark PDF. It places one faint mark across the document in one go, so the words underneath stay readable.
Covering is not removing
This is the one thing on this page that can actually hurt you. Everything you add sits on top of the page. Text under a box, a highlight or a picture is still in the file and can still be selected, searched and copied straight out of it by anyone who receives it.
So a black rectangle over an account number is a black rectangle over an account number, not a deleted account number. If information must not leave with the document, remove the page it is on, or use software that redacts — which means rewriting the page's contents, not painting over them.
Why a highlight can be taken off
Highlights, underlines and strike-throughs are written as real PDF annotations, so any reader can select one, change its color or remove it. That is deliberate.
The alternative — painting a colored rectangle onto the page — would be permanent and would sit over the words rather than marking them, which is the wrong thing in both directions. A mark that a reader can work with is what marking up a document is for.
Which alphabets you can type in
Latin and Devanagari, from a font bundled with the tool so that nothing is fetched from the internet while you work. Text in a script neither covers is refused rather than written as empty boxes, so you find out while you are typing rather than after you have downloaded the file.
What to know before you start
- The document's own text is never touched. It stays exactly as it is, and stays selectable and searchable, which is also why nothing you add can hide it.
- A locked PDF has to be unlocked first, with the password, before anything can be added to it.
- Nothing is uploaded. Everything you add is written onto the page in your browser and the file never leaves the device you are on.