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Does flattening a PDF kill its hyperlinks?

You are about to flatten something. A filled-in form that has to go out as a record, or a report with comments on it that need pressing into the page. The document also has links in it — a contents page that jumps, a URL in the footer, forty citations that a reader is meant to click.

So you searched to check whether flattening takes the links with it, and page one is a wall of articles about how to remove hyperlinks from a PDF, which is the opposite of what you asked. Behind them are two Adobe forum threads from people asking your exact question, neither of them answered well.

Here is the honest version. With our Flatten PDF tool, no: links are deliberately left working, and the run tells you how many. But "flatten" names three different operations depending on who is doing it, and one of them does kill links — while leaving them looking exactly as they did. That is the part worth two minutes.

This is the fact everything else follows from, and no page ranking for this query states it.

The blue underlined text is page content. When Word or InDesign or LaTeX writes out a link, it draws the words in a blue colour and strokes a line under them, in the same content stream as every other glyph on the page. Those instructions are ordinary drawing, indistinguishable from a blue heading.

The clickable part is an annotation. Separately, the producer adds an entry to the page's annotation list: a /Link object holding a rectangle and an action. /A with a /URI for a web address, /Dest for a jump to somewhere in this same document. It has no colour, no border width and nothing to draw. It is a hit area, floating over the words, and a reader turns the pointer into a hand when you are inside it.

Two consequences fall straight out of that split.

The first is why the "remove hyperlinks" articles have such unhappy comment sections. Delete the annotation and the blue underline stays exactly where it was, so the document still looks full of links and everybody assumes the tool failed.

The second is the answer to your question. Flattening means taking an object's appearance and writing it into the page so the object is no longer needed. A link has no appearance. There is nothing to write. Flattening a link cannot press anything into the page — it can only delete the annotation, which loses the click and keeps the look. That is the worst of both outcomes, and it is purely a loss.

Why ours leaves them alone, and what it says

Our flatten walks the annotations on each page and asks each one for its normal appearance stream. Form widgets and comments have one, so it is drawn into the page's content at the rectangle the object occupied and the object is deleted — the same mechanism a reader uses to display it, which is why the result holds up in software neither of you has heard of.

Anything with the Link subtype is put straight into the keep pile before that question is asked. When you tick the comments option, the notes count them for you: "7 links were left working."

Flattening only the form fields — the default — cannot touch links either, because a link is not a form widget and the flattening runs over the form's own fields. You get no line about links in the notes in that case, because nothing looked at them. Silence there means untouched, not checked.

The query has no universal answer because the word covers three unrelated jobs.

  1. Pressing annotations into the page, which is what we do and what most web tools mean. Whether links survive is a decision the implementer makes. Acrobat's version — the Preflight fixup, and the doc.flattenPages() JavaScript behind it — clears the annotation list wholesale, links included. That is why the threads you found exist, and why the workaround posted in them is a script that records every link's rectangle and destination first and adds them back afterwards.
  2. Re-rendering the document, which is what "just print it to PDF" means. The printing path speaks only in marks on paper and has no vocabulary for "this rectangle points at page 40", so every link goes, along with the bookmarks and the tags. The comparison is worth reading before you take that advice.
  3. Transparency flattening, which is a prepress operation on overlapping transparent objects. Different word, same spelling, nothing to do with annotations. We do not do it at all.

So if someone tells you flattening killed their links, they are almost certainly describing one or two, and they are right about their tool.

Worth knowing, because people arrive here having blamed the wrong step.

Our inspector reads page count, page sizes, encryption, tagging, the form field count and whether there is a real text layer, all in the browser — but it does not count links, which is worth saying plainly since this is the one page where you want that number.

Three ways to get it:

Do the count before and after and the question stops being a matter of trust.

Sometimes that is the job — a draft going outside with internal URLs in it, or a filing where live links are not wanted. Flattening is not the tool for that in either direction. Use Remove annotations from PDF with "links only": it strips the annotations and leaves the text, layout and pagination untouched, because nothing visible was ever involved. The blue underline will still be there afterwards, and that is not a failure — changing the look means editing the page itself in the PDF editor.

Nor does a password help. Password protect PDF encrypts the file and sets flags for printing, copying, editing and commenting. There is no flag for clicking, and a link in an encrypted document works exactly as it did.

The order to do this in

If the document is going out as a production or a filing, the sequence that keeps everything is: flatten first, then stamp with Bates numbering — which draws its references into the page content rather than adding annotations, so it neither disturbs the links nor adds any — then set a password if you need one, and sign last, because every one of those steps rewrites the file.

Done that way, the answers are permanent, every page has its reference, and the forty citations still go where the author put them.

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