5 ms·

Other than fillable forms, which is sometimes very important, I don't see how PDF is much of an improvement over PostScript (which came first).

by xscott 6y ago

thrtythreeforty 6y ago
Embedded fonts are a big one. PDF lets you embed straight TrueType/OpenType, preserving all the ligatures, kerning, etc. With Postscript you have to convert. Maybe this would be hassle free, but I'd be willing to bet there'd be a lot of edge cases that prevent it from Just Working.
- microcolonel 6y ago
  > preserving all the ligatures, kerning Far as I can tell, most of the time (all of the time?) PDFs just seem to throw out this information, and manually select and place glyphs.
dragontamer 6y ago
PDFs work on Windows. Postscript just never had a big Windows adoption rate. From my understanding, PDF is largely based on Postscript. PDF is to Postscript as HTML5 is to XHTML or HTML4.
jcrawfordor 6y ago
A very simple answer: Xorg has integrated PostScript support which makes rendering .ps files very easy on Linux. Very few tools were ever developed to do this on Windows, to the extent that using Ghostscript ported from Linux is still a common approach. It's still a pain to deal with PostScript files on Windows, and obvious tricks like using ports of Linux viewers that support .ps generally don't work on Windows because those viewers were just leaning on Xorg to do the hard part. PDF would have a similar problem, but Adobe leveraged their previous work on other products so they basically already had the rendering engine for Windows and it gained traction there. Keep in mind that both Postscript and PDF were principally designed by Adobe. Adobe designed both because they were intended for different purposes, and this stands today.
- kbr2000 6y ago
  Hey, I'd like to read more about this integrated PostScript support for Xorg, can you point me in the right direction please? Tnx
  - lmz 6y ago
    There you go: https://docs.oracle.com/cd/E19683-01/816-0279/dps-91433/index.html https://docs.oracle.com/cd/E19683-01/816-0279/dps-91433/inde... Except it's not Xorg but Sun's own server, and it's not Linux but Solaris.
  - jcrawfordor 6y ago
    The feature is called display postscript (DPS), it is basically gone today and was not widespread on Linux, but Adobe maintained a version which they commonly packaged with their products and was a key part of the genesis of the PDF format. These days it is mostly replaced by ghostscript.
rietta 6y ago
PDFs also serve as a decent interchange format for dropping "signatures" onto a document. These are acceptable in court and in a format that regular business people understand. This is important for digitized contracts that can then also be archived by both parties.
- ThePadawan 6y ago
  My $0.02 on this: A work colleague worked on a document signing solution for a client once. Legally, at the time (and I hope this has improved), when a person added their digital signature to a document, that meant that they signed that exact version (read: hash of all the bytes) of the document. That meant that PDF was sort-of problematic for the use case that the customer required: Giving the customer an A4 version to keep for their documentation was important - but having an A4 version on screen made for terrible scaling UX on mobile and tablet devices. The fact that PDF is more than just text+formatting in that manner was a real hindrance at that point in time (2017). (I'd be happy to know if I got any of this wrong after only hearing about it second-hand. This was in Switzerland, if this affects which laws were relevant at the time.).
  - pfranz 6y ago
    I think it's been around since the early 2000s, but a few months ago I got very tripped up by this for the first time. I got a PDF I needed to sign and send back (I usually drop and image of my signature and fax or reply). I actually needed to submit a bunch of these forms with varying dates. I couldn't open the PDF with macOS' Preview or any web reader (which happens time to time). I reluctantly downloaded Acrobat Reader. Filled it out, "signed it" and tried to change the date and Save As. It wouldn't let me and it wasn't clear why. I thought I just didn't know how to undo or select and delete the signature because I'm used to PDFs being text + images. It turns out to be a feature where adding a "signature" locks the document. They suggest if you need to modify it you request a new document. I'm probably reading the spec wrong, but it might have been added in PDF 1.5 (Aug 2003?)
    - quietbritishjim 6y ago
hnick 6y ago
One problem is that Postscript is Turing complete, so it can be unreliable to parse. Not a great outcome if you just want to view a document. However, in reality I've often found it easier to write throwaway perl scripts to analyse/modify PS files rather than PDF. Writing a tool to target a set of PS files made by the same process usually isn't too hard unless there is something really unique going on - but it can be a problem generalising it to any random PS file. PDF is more structured so it can be easier to make general purpose tools, but in my line of work we prefer version 1.4 since the later versions add bloat that isn't necessary for print. It's also usually easier to consider them append-only, it's trivial to add content but editing is a lot harder due to offsets and references.

Other than fillable forms, which is sometimes very important, I don't see how PDF is much of an improvement over PostScript (which came first).

by xscott 6y ago

Other than fillable forms, which is sometimes very important, I don't see how PDF is much of an improvement over PostScript (which came first).

thrtythreeforty 6y ago

Embedded fonts are a big one. PDF lets you embed straight TrueType/OpenType, preserving all the ligatures, kerning, etc. With Postscript you have to convert. Maybe this would be hassle free, but I'd be willing to bet there'd be a lot of edge cases that prevent it from Just Working.

microcolonel 6y ago
> preserving all the ligatures, kerning Far as I can tell, most of the time (all of the time?) PDFs just seem to throw out this information, and manually select and place glyphs.

dragontamer 6y ago

PDFs work on Windows. Postscript just never had a big Windows adoption rate. From my understanding, PDF is largely based on Postscript. PDF is to Postscript as HTML5 is to XHTML or HTML4.

jcrawfordor 6y ago

A very simple answer: Xorg has integrated PostScript support which makes rendering .ps files very easy on Linux. Very few tools were ever developed to do this on Windows, to the extent that using Ghostscript ported from Linux is still a common approach. It's still a pain to deal with PostScript files on Windows, and obvious tricks like using ports of Linux viewers that support .ps generally don't work on Windows because those viewers were just leaning on Xorg to do the hard part. PDF would have a similar problem, but Adobe leveraged their previous work on other products so they basically already had the rendering engine for Windows and it gained traction there. Keep in mind that both Postscript and PDF were principally designed by Adobe. Adobe designed both because they were intended for different purposes, and this stands today.

kbr2000 6y ago
Hey, I'd like to read more about this integrated PostScript support for Xorg, can you point me in the right direction please? Tnx
- lmz 6y ago
  There you go: https://docs.oracle.com/cd/E19683-01/816-0279/dps-91433/index.html https://docs.oracle.com/cd/E19683-01/816-0279/dps-91433/inde... Except it's not Xorg but Sun's own server, and it's not Linux but Solaris.
- jcrawfordor 6y ago
  The feature is called display postscript (DPS), it is basically gone today and was not widespread on Linux, but Adobe maintained a version which they commonly packaged with their products and was a key part of the genesis of the PDF format. These days it is mostly replaced by ghostscript.

rietta 6y ago

PDFs also serve as a decent interchange format for dropping "signatures" onto a document. These are acceptable in court and in a format that regular business people understand. This is important for digitized contracts that can then also be archived by both parties.

ThePadawan 6y ago
My $0.02 on this: A work colleague worked on a document signing solution for a client once. Legally, at the time (and I hope this has improved), when a person added their digital signature to a document, that meant that they signed that exact version (read: hash of all the bytes) of the document. That meant that PDF was sort-of problematic for the use case that the customer required: Giving the customer an A4 version to keep for their documentation was important - but having an A4 version on screen made for terrible scaling UX on mobile and tablet devices. The fact that PDF is more than just text+formatting in that manner was a real hindrance at that point in time (2017). (I'd be happy to know if I got any of this wrong after only hearing about it second-hand. This was in Switzerland, if this affects which laws were relevant at the time.).
- pfranz 6y ago
  I think it's been around since the early 2000s, but a few months ago I got very tripped up by this for the first time. I got a PDF I needed to sign and send back (I usually drop and image of my signature and fax or reply). I actually needed to submit a bunch of these forms with varying dates. I couldn't open the PDF with macOS' Preview or any web reader (which happens time to time). I reluctantly downloaded Acrobat Reader. Filled it out, "signed it" and tried to change the date and Save As. It wouldn't let me and it wasn't clear why. I thought I just didn't know how to undo or select and delete the signature because I'm used to PDFs being text + images. It turns out to be a feature where adding a "signature" locks the document. They suggest if you need to modify it you request a new document. I'm probably reading the spec wrong, but it might have been added in PDF 1.5 (Aug 2003?)
  - quietbritishjim 6y ago

hnick 6y ago

One problem is that Postscript is Turing complete, so it can be unreliable to parse. Not a great outcome if you just want to view a document. However, in reality I've often found it easier to write throwaway perl scripts to analyse/modify PS files rather than PDF. Writing a tool to target a set of PS files made by the same process usually isn't too hard unless there is something really unique going on - but it can be a problem generalising it to any random PS file. PDF is more structured so it can be easier to make general purpose tools, but in my line of work we prefer version 1.4 since the later versions add bloat that isn't necessary for print. It's also usually easier to consider them append-only, it's trivial to add content but editing is a lot harder due to offsets and references.