I’m not sure if they were ever designed to be immutable, but that’s what a lot of people use it for because it’s harder to edit them. But there are programs that can edit PDFs. The main issue is I’m not aware of any free ones, and a lot of the alternatives don’t work as well as Adobe Acrobat which I hate! It’s always annoying at work when someone gets sent a document that they’re expected to edit and they don’t have an Acrobat license!
PDFs can contain a vast amount of different Image information, but often a good software that can edit vector data opens PDFs for editing easily. It might convert not embedded Fonts in paths and rasterize some transparency effects though.
So Inkscape might work.
I’m assuming that will work similar to Microsoft Word where it’s fine for basic PDFs but if there are a lot of tables or images it can mess up the document?
think of it as though pdf is the container - it can contain all sorts of different data. I'd say you got real lucky being able to edit one with Writer without issues.
No, it's too preserve formatting when distributed. Editing is absolutely possible, always were, it's just annoying to parse the structure when trying to preserve the format as you make changes
No, although there's probably a culture or convention around that.
Originally the idea was that it's a format which can contain fonts and other things so it will be rendered the same way on different devices even if those devices don't have those fonts installed. The only reason it's not commonly editable that I'm aware of is that it's a fairly arcane proprietary spec.
Now we have the openspec odt which can embed all the things, so pdf editing just doesn't really seem to have any support.
The established conventions around pdfs do kind of amaze me. Like contracts get emailed for printing & signing all the time. In many cases it would be trivial to edit the pdf and return your edited copy which the author is unlikely to ever read.