[cylemons]

PDF is more like a glorified svg format than a word format.

It only contains info on how the document should look but so semantic information like sentences, paragraphs, etc. Just a bag of characters positioned in certain places.

[Macha]

Sometimes the characters aren’t even characters, just paths

[cylemons]

Wouldn't that be very space inefficient to repeat the paths every time a letter appears in the file? Or you mean that glyph Ids don't necessarily map to Unicode?

[user____name]

Outlines are just a practical way of handling less common display cases.

Just to give a practical example. Imagine a Star Wars advert that has the Star Wars logo at the top, specified in outlines because that's what every vector logo uses. Below it the typical Star Wars intro text stretched into perspective, also using outlines, because that's the easiest (display engine doesn't need complicated transformation stack), efficient to render (you have to render the outlines anyway), and most robust way (looks the same everywhere), way of implementing transformations in text. You also don't have to supply the font file, which comes with licensing issues, etc. Also whenever compositing and transparency are involved, with color space conversion nonsense, it's more robust to "bake" the effect via constructive geometry operations, etc, to prevent display issues on other devices, which are surprisingly common.

[manishsn]

sometimes in fancy articles you might see the first letter is large and ornate which is most likely a path also like you said glyph IDs always don't necessarily map to unicode or the creator can intentionally mangle the 'to unicode' map of Identity-H embedded font in the pdf if he is nasty