There are two kinds of PDF feedback.
The first is an email that says “see my comments in the doc” with an attached PDF containing yellow sticky notes, red text boxes, strikethrough lines, and margin annotations created in Adobe Acrobat Pro. It costs the sender $55/month. The recipient can read the comments in any PDF viewer. The system works. It’s just expensive for the person doing the marking up.
The second is an email that says “see attached” with a PDF where someone has opened the file in Preview, drawn wobbly freehand circles around the problematic areas, added text boxes that overlap the content, and saved it as a flattened image — meaning the annotations can’t be selected, responded to, or removed. The system doesn’t work. But it was free.
This is the markup gap. The space between “professional but expensive” and “free but terrible.” And it’s wider than it needs to be.
PDF markup is annotation — adding a layer of commentary on top of an existing document without changing the document itself. Highlights, text notes, shapes, arrows, freehand drawings, stamps, text boxes. None of these require complex software to implement. The PDF specification has supported annotation objects since the 1990s. The technical foundation is there. The accessibility isn’t.
What most people need from a markup tool is straightforward: open a PDF, highlight sections, add comments, draw attention to specific areas, and save the result as a PDF that anyone else can open and read. The comments should be real annotation objects — selectable, deletable, printable separately — not flattened pixels burned into the page.
That’s it. Not version control. Not collaborative editing. Not comment threads with @mentions and due dates. Just: here’s the document, here are my notes, here’s the file.