Hacker News Reader

Comment by wild_pointer | Hacker News Reader

That'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.

View on HN

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.

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.

It's still what a PDF editor, as it says in the title, would do. With a quick Google I found one that I hadn't heard about before, and it let me edit some text and save it for free.

Ask yourself, why would someone spend money on bandwidth for me to download something for free...

PDF editor is used as a broadly encompassing term. Yes, other tools can edit existing text, but they upload your PDF to their servers, so it's not private if that's something you care about.

There isn't anything off the shelf that enables editing existing text in the browser, but it's something I'll build from scratch. So you'll be able to edit existing PDF text without compromising privacy.

This can if I remember correctly (can't check now), but it's a POC and not a finished product https://github.com/ShizukuIchi/pdf-editor

Yes, and alongside formatting challenges, PDFs commonly only include the glyphs from the font that are actually used in the document.

So if you had PDF with "Hello World" on it, you could feasibly change it to "Hello Hello", but wouldn't be able to change it to "Goodbye World" (as the glyphs for "G", "b", "y", and "e" are not included in the PDF)

Sure, you could do a bit of detective work to figure out which font it was from the glyphs or something and lookup and insert new glyphs into the PDF, but I can't imagine a generic PDF editor being capable of doing this for you.

Some editors get around this but just straight up switching the font(s) for the whole PDF, so they'll look different after saving.

Sejda.com does it. Though its free one is severely crippled

PDF is really not a format designed for editing, of text content in particular. It’s only possible in limited circumstances.

Reply on news.ycombinator.com