alt Hacker NewsThat's the problem with all the pdf editors available out there. I guess adding stuff is much easier than editing existing stuff which you didn't add, and can be laid out in a gazillion ways, because PDF is a format for viewing and printing, not for editing.
I had a period when I worked with lots of documents. I could only find one fairly decent PDF editor which deserves to be called that way. I could use it to open any PDF and delete an existing element, or change text in an existing field. Sometimes things behaved funny, for example a text field can have each letter in a separate block, but I assume the tool did what it could within reasonable effort. It worked fine for me overall.
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Editing text in PDFs is _really_ hard compared to other document formats because most PDFs don't really encode the "physics" of the document. I.e. there isn't a notion of a "text block with word wrapping," it's more "glyphs inserted at location X with font Y."
If the PDF hasn't been made accessible, you have to do a lot of inferencing based on the layout about how things are grouped and how they should flow if you want to be able to make meaningful edits. Not impossible (Acrobat does it), but very challenging.
It's part of the legacy of PDF as a format for presentation and print jobs, rather than typesetting.
PDF is really not a format designed for editing, of text content in particular. It’s only possible in limited circumstances.
PDF was basically created as a final presentation format, it's essentially append-only by design, which is why you hear so often of redactions just marking up a white/black box over text.
You can edit text streams, which needs a decompress/recompress, messes up all the object reference offsets for the entire file, potentially adds or removes characters to the subset font, which may not be referenced by the glyphs but a number instead to intentionally break copy/paste/scrape (e.g. 'a' is not 'a' in the text stream, but a random number), etc. Assuming the text is even marked up as strings, and not individually positioned characters with nested offset co-ordinate scaling to further muddy the waters.
The fact so many people want to edit PDFs probably indicates a design flaw on Adobe's side, when considering what customers really want.