QuokkaEdit the text in a PDF
Open a file above, click the line you want to change, and type over it. The replacement goes into the document itself, in the font that was already on the page.
Why most editors change the font
PDFs almost never carry a whole typeface. They carry a subset: only the characters the document happened to use, and often no usable character map either. An editor that cannot read that subset has two options and both are visible. Swap a different font in for the whole line, or draw the characters it cannot find as empty boxes.
Quokka reads each font's own character codes out of the file and writes with those, so the glyphs are the ones already on the page. Where a character genuinely is not in the subset it borrows from a matched face, and tells you which ones it had to borrow.
What you can change
Any line of real text, on any page. Hover one to see its font and size. Edits undo and redo, and nothing touches your original file: the edited copy only exists once you press Download.
What it will not do
Text does not reflow. Type something longer than the line it replaces and it runs into whatever sits to the right, which is true of every PDF editor rather than just this one. Scanned pages have no text layer to click, so they need OCR first; you will get a note when one turns up. Editing a digitally signed PDF invalidates the signature, and you are warned before you start.
Is it really free
Yes, with no account and no file limit. Editing existing text is the feature most online editors keep for a paid plan: Adobe's free tier only lets you annotate, and Smallpdf asks for Pro. It is free here because there is no server bill to cover, since the work happens on your own machine.