3 ms·

How to create accessible PDFs from the start

106 points by leephillips 1y ago

ozim 11mo ago
Have to say I really liked reading the article on mobile. I have smaller phone even but layout was good an spacing was great. Black text on white background not some grayish to look different but perfectly legible.
elric 11mo ago
> It will be read in the wrong order I really dislike it when this happens. This also affects copy/pasting. This typically seems to happen with LaTeX-style two-column layouts, where columns are supposed to be read top to bottom, left to right, but tools end up reading paragraphs from left to right, top to bottom. It's infuriating. PDFs suck. And it's awful that they're the least bad option for a lot of things.
dvh 11mo ago
I've noticed a very lagy performance when reading specifically Texas instrument datasheets, I scroll 2 pages and bam 5s lag, then it usually works or lags occasionally. I passed the PDF through some gpt-concocted ghostscript woodoo and then they work just fine: gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \ -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH \ -sOutputFile=output.pdf input.pdf
- mmooss 11mo ago
  How does that script change the PDF? Does -dPDFSETTINGS=/ebook do something? Is simply rewriting it in ghostscript making a difference?
  - dvh 11mo ago
    I think the 1.4 does the most.
jiehong 11mo ago
TIL: PDF/UA is a thing! While reading the article I could only think that all this semantic stuff is what html is about! So, I think it makes more sense to do what arxiv is doing: providing a html version of articles on top of pdfs. I’d even say html should be the source and the PDF should be generated from it instead.
- robin_reala 11mo ago
  You won’t be able to generate semantic HTML from inaccessible PDF, that needs to be there from day one.
chanux 11mo ago
I wonder if some of these accessibility features help LLMs (Given the programs that process PDFs to feed LLMs account for those.)
- lblume 11mo ago
  Sure. But it also helps humans, and I'd guess currently more so.
  - chanux 11mo ago
    Did my comment come in a negative tone? It was more of a genuine question, if it can be useful for machines while not being "visible". This thinking is a slippery slope though, because it can be stretched to a point where it defeats the original purpose.
ethin 11mo ago
IMO PDFs should just be gone. Nobody should use them. They are a solution in search of a problem. The most common argument I hear is "well we need document fidelity!" But IMO this completely ignores the fact that this just isn't needed when we have digital signatures and a PKI and certificates and all that to prove that a document hasn't been tampered with. Making sure a document appears the same on any kind of device/OS or whatever would be a great idea in theory if the way it was done was actually thought through, but it wasn't and now the PDF format is even worse than HTML is (and that's really saying something). Every single time I have had to interact with a PDF it has always been a total disaster. Don't even get me started on the clusterfuck that is PDF forms.
- ozim 11mo ago
  PDF is fine as output format and for archiving. Thing is people want to do bunch of things they shouldn’t with PDF like automated parsing, editing or adding forms to it. Ideally you should have an API or other structured data to pass around but of course life is more complicated. Like PDF is all you get because API would cost more than it makes sense to do bad job parsing PDF.
- wongarsu 11mo ago
  The problem was "have documents that look the same on any device, including printed paper and computer screens", and the approach was "PostScript does that for printers, let's simplify it and make it more universal". Both the problem it's solving and the approach were fine, maybe even great. Since then over three decades have passed, pdf has gained a plethora of features, some less well thought out than others, and real-world requirements are completely different than they were in the early 90s. If we were to invent pdf today it would likely look completely different. But it's still good enough that it's hard for a new format to offer an advantage compelling enough to replace pdf.
  - ethin 11mo ago
    Right, but that's what I'm getting at: PDF is just a terrible format all round. People do things with it that have nothing to do with document preservation. We have PDF forms, we have PDFs able to execute arbitrary JS (which can modify the rendering of the document, completely defeating the entire reason for the format existing)... Like IMO the format just has no reason to exist/be used anymore given how bloated and over-complicated it is.
miki123211 11mo ago
Typst doesn't (yet) do math accessibility I think, and Math is a lot of what it is about. Wondering why they omitted that information from a blog post promoting Typst for accessibility use cases...
thangalin 11mo ago
#show strong: set text(fill: blue) Join us for a David Lynch double feature with *Mulholland Drive* and *Inland Empire* next Tuesday at 8:15 PM. I didn't realize Typst mixes content and presentation. Presumably, Typst allows including styles from external sources, much like the HTML/CSS split? ConTeXt has also been making strides in creating accessible PDF files: * https://meeting.contextgarden.net/2024/talks/hans+mikael/context-2024-accessibility.pdf https://meeting.contextgarden.net/2024/talks/hans+mikael/con... * https://wiki.contextgarden.net/Input_and_compilation/Accessibility https://wiki.contextgarden.net/Input_and_compilation/Accessi...
- klauserc 11mo ago
  Isn't that example the exact opposite of mixing content and presentation? The * notation applies the strong [emphasis] tag, the show rule (re-)defines the presentation. Ideally you would of course separate the two into separate files (template + content). In my time using Typst, I found that Typst makes it possible/easy to make content even more abstract: write the content as a "data structure" and then present parts of it in various places around your document. For instance to list quantity/weight of a parts description in a parts index at the end.
  - thangalin 11mo ago
    > Ideally you would of course separate the two into separate files (template + content). Exactly: If instructions for how to style the content are in the same file as the content, then that is mixing content _with_ presentation logic. Avoiding this approach to documentation is what I alluded to in writing, "Presumably, Typst allows including styles from external sources."

106 points by leephillips 1y ago

ozim 11mo ago

Have to say I really liked reading the article on mobile. I have smaller phone even but layout was good an spacing was great. Black text on white background not some grayish to look different but perfectly legible.

elric 11mo ago

> It will be read in the wrong order I really dislike it when this happens. This also affects copy/pasting. This typically seems to happen with LaTeX-style two-column layouts, where columns are supposed to be read top to bottom, left to right, but tools end up reading paragraphs from left to right, top to bottom. It's infuriating. PDFs suck. And it's awful that they're the least bad option for a lot of things.

dvh 11mo ago

I've noticed a very lagy performance when reading specifically Texas instrument datasheets, I scroll 2 pages and bam 5s lag, then it usually works or lags occasionally. I passed the PDF through some gpt-concocted ghostscript woodoo and then they work just fine: gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \ -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH \ -sOutputFile=output.pdf input.pdf

mmooss 11mo ago
How does that script change the PDF? Does -dPDFSETTINGS=/ebook do something? Is simply rewriting it in ghostscript making a difference?
- dvh 11mo ago
  I think the 1.4 does the most.

jiehong 11mo ago

TIL: PDF/UA is a thing! While reading the article I could only think that all this semantic stuff is what html is about! So, I think it makes more sense to do what arxiv is doing: providing a html version of articles on top of pdfs. I’d even say html should be the source and the PDF should be generated from it instead.

robin_reala 11mo ago
You won’t be able to generate semantic HTML from inaccessible PDF, that needs to be there from day one.

chanux 11mo ago

I wonder if some of these accessibility features help LLMs (Given the programs that process PDFs to feed LLMs account for those.)

lblume 11mo ago
Sure. But it also helps humans, and I'd guess currently more so.
- chanux 11mo ago
  Did my comment come in a negative tone? It was more of a genuine question, if it can be useful for machines while not being "visible". This thinking is a slippery slope though, because it can be stretched to a point where it defeats the original purpose.

ethin 11mo ago

IMO PDFs should just be gone. Nobody should use them. They are a solution in search of a problem. The most common argument I hear is "well we need document fidelity!" But IMO this completely ignores the fact that this just isn't needed when we have digital signatures and a PKI and certificates and all that to prove that a document hasn't been tampered with. Making sure a document appears the same on any kind of device/OS or whatever would be a great idea in theory if the way it was done was actually thought through, but it wasn't and now the PDF format is even worse than HTML is (and that's really saying something). Every single time I have had to interact with a PDF it has always been a total disaster. Don't even get me started on the clusterfuck that is PDF forms.

ozim 11mo ago
PDF is fine as output format and for archiving. Thing is people want to do bunch of things they shouldn’t with PDF like automated parsing, editing or adding forms to it. Ideally you should have an API or other structured data to pass around but of course life is more complicated. Like PDF is all you get because API would cost more than it makes sense to do bad job parsing PDF.
wongarsu 11mo ago
The problem was "have documents that look the same on any device, including printed paper and computer screens", and the approach was "PostScript does that for printers, let's simplify it and make it more universal". Both the problem it's solving and the approach were fine, maybe even great. Since then over three decades have passed, pdf has gained a plethora of features, some less well thought out than others, and real-world requirements are completely different than they were in the early 90s. If we were to invent pdf today it would likely look completely different. But it's still good enough that it's hard for a new format to offer an advantage compelling enough to replace pdf.
- ethin 11mo ago
  Right, but that's what I'm getting at: PDF is just a terrible format all round. People do things with it that have nothing to do with document preservation. We have PDF forms, we have PDFs able to execute arbitrary JS (which can modify the rendering of the document, completely defeating the entire reason for the format existing)... Like IMO the format just has no reason to exist/be used anymore given how bloated and over-complicated it is.

miki123211 11mo ago

Typst doesn't (yet) do math accessibility I think, and Math is a lot of what it is about. Wondering why they omitted that information from a blog post promoting Typst for accessibility use cases...

thangalin 11mo ago

#show strong: set text(fill: blue) Join us for a David Lynch double feature with *Mulholland Drive* and *Inland Empire* next Tuesday at 8:15 PM. I didn't realize Typst mixes content and presentation. Presumably, Typst allows including styles from external sources, much like the HTML/CSS split? ConTeXt has also been making strides in creating accessible PDF files: * https://meeting.contextgarden.net/2024/talks/hans+mikael/context-2024-accessibility.pdf https://meeting.contextgarden.net/2024/talks/hans+mikael/con... * https://wiki.contextgarden.net/Input_and_compilation/Accessibility https://wiki.contextgarden.net/Input_and_compilation/Accessi...

klauserc 11mo ago
Isn't that example the exact opposite of mixing content and presentation? The * notation applies the strong [emphasis] tag, the show rule (re-)defines the presentation. Ideally you would of course separate the two into separate files (template + content). In my time using Typst, I found that Typst makes it possible/easy to make content even more abstract: write the content as a "data structure" and then present parts of it in various places around your document. For instance to list quantity/weight of a parts description in a parts index at the end.
- thangalin 11mo ago
  > Ideally you would of course separate the two into separate files (template + content). Exactly: If instructions for how to style the content are in the same file as the content, then that is mixing content _with_ presentation logic. Avoiding this approach to documentation is what I alluded to in writing, "Presumably, Typst allows including styles from external sources."