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So you want to modify the text of a PDF by hand (2020)

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Re: So you want to modify the text of a PDF by hand (2020)

#61

Post by gobdovan »

aidos wrote: post #5

This topic comes up periodically as most people think PDFs are some impenetrable binary format, but they’re really not. They are a graph of objects of different types. The types themselves are well described in the official spec (I’m a sadist, I read it for fun). My advice is always to convert the pdf to a version without compressed data like the author here has. My tool of choice is mutool (mutool clean -d in.pdf ou…

If you find pleasure in something that gives you pain, you're a masochist. A sadist likes inflicting pain onto others. Since you seem that you like helping people I'd say it's more likely you're the former. I appreciate the mutool advice!

Re: So you want to modify the text of a PDF by hand (2020)

#62

Post by mistrial9 »

dylan604 wrote: post #46
pwg wrote: post #37

Earlier quoted context omitted.

> It is a shame Adobe designed a format so hard to work with PDF was not designed to be editable, nor for anyone to "work with" it in that way. It was designed (at least the original purpose circa 1989) to represent printed pages electronically in a format that would view and print identically everywhere. In fact, the initial advertising for the "value" of the PDF format was exactly this, no matter where a recipient…

Wasn't the PDF format based on the Illustrator format? The weird thing to me is people using a distribution format as an original source. It's right up there with video cameras shooting an acquisition source as an MP4 and all of the negative baggage that comes with that.

1.4.4 Portable Document Format (PDF) Adobe has specified another format, PDF, for portable representation of electronic documents. PDF is documented in the Portable Document Format Reference Manual. PDF and the PostScript language share the same underlying Adobe imaging model. A document can be converted straightforwardly between PDF and the PostScript language; the two representations produce the same output when printed. However, PDF lacks the general-purpose programming language framework of the PostScript language. A PDF document is a static data structure that is designed for efficient random access and includes navigational information suitable for interactive viewing.

-- https://www.adobe.com/jp/print/postscript/pdfs/PLRM.pdf

Re: So you want to modify the text of a PDF by hand (2020)

#63

Post by haolez »

aidos wrote: post #5

This topic comes up periodically as most people think PDFs are some impenetrable binary format, but they’re really not. They are a graph of objects of different types. The types themselves are well described in the official spec (I’m a sadist, I read it for fun). My advice is always to convert the pdf to a version without compressed data like the author here has. My tool of choice is mutool (mutool clean -d in.pdf ou…

That's awesome. I'm relying a lot on Amazon Textract for my PDF parsing needs.

Do you have any other insights on how to do a good job at that natively, i.e. without a cloud provider? Especially when dealing with tables.

Re: So you want to modify the text of a PDF by hand (2020)

#64

Post by hnick »

enriquto wrote: post #17

You can do this: pdf2ps a.pdf # convert to postscript "a.ps" vim a.ps # edit postscript by hand ps2pdf a.ps # convert back to pdf Some complex pdf (with embedded javascript, animations, etc) fail to work correctly after this back and forth. Yet for "plain" documents this works alright. You can easily remove watermarks, change some words and numbers, etc. Spacing is harder to modify. Of course you need to know some po…

This is essentially how we used to do it for some "print-ready" jobs at a mailhouse I worked at. Usually we'd use proper tools to produce documents ready to print, but sometimes clients thought they knew better and would send us PDFs. It was more effort to work with those usually, and had a higher chance of errors.

Even if the output was correct, we still needed to re-order pages, apply barcodes for mail machine processing and postal sorting, and produce reports - which usually involved text scraping off the page to get an address via perl and other tools. Much easier in PS than PDF usually, but sometimes very unreliable when e.g. their PDFs were 'secure' and didn't have correct glyph mappings.

In the worst cases, they would supply single document PDFs, and merging those would cause an explosion of subset fonts in the output which would fill the printer's memory and crash it. When I stopped working in the area, I think there still wasn't a useful tool to consolidate and merge subset fonts known to come from the same parent font - it would have been a very useful tool and should be possible but I didn't have the time or knowledge to look into it.

Re: So you want to modify the text of a PDF by hand (2020)

#65

Post by kccqzy »

haolez wrote: post #63
aidos wrote: post #5

This topic comes up periodically as most people think PDFs are some impenetrable binary format, but they’re really not. They are a graph of objects of different types. The types themselves are well described in the official spec (I’m a sadist, I read it for fun). My advice is always to convert the pdf to a version without compressed data like the author here has. My tool of choice is mutool (mutool clean -d in.pdf ou…

That's awesome. I'm relying a lot on Amazon Textract for my PDF parsing needs. Do you have any other insights on how to do a good job at that natively, i.e. without a cloud provider? Especially when dealing with tables.

PDF format does not give you enough semantic information to understand there is a table. The stream contains instructions such as moving to a coordinate, adding some text, adding some lines. No tool can extract tables with 100% precision.

Re: So you want to modify the text of a PDF by hand (2020)

#66

Post by kccqzy »

mx_02 wrote: post #60
schlowmo wrote: post #45

PDF is such a weird format. Not so long ago I had to write some Java code for manipulating PDFs: find a string, remove it and place an image at the former string position. I should have known better as I thought "Well, how hard can that be?” What followed was a deep dive down the rabbit hole, a lot of fiddling with the same tools the author of this gist is using trying to make sense of it all. The final solution work…

> "Well, how hard can that be?” Very hard? I worked on a tool that generated PDFs based on API responses. The tool added charts from the api data. Those PDFs were reports with some hardcoded text. Yesh what a fun ride that was.

Generating PDFs are incredibly easy. I just generate LaTeX and run it through lualatex. When precise positioning is needed, I just use a giant tikzpicture.

Re: So you want to modify the text of a PDF by hand (2020)

#67

Post by kccqzy »

yboris wrote: post #58

Semi-related(?) - I created a repository to convert PDF to JPG and back to PDF: https://github.com/whyboris/PDF-to-JPG-to-PDF A government form didn't have editable fields that needed to be filled out. And editing the PDF was impossible (password protection). This was my solution.

On macOS using Preview you can add textual comments on otherwise uneditable PDFs. Then you can simply print the commented PDF as a new PDF.

Converting to JPG unnecessarily rasterizes text and introduces ugly compression artefacts.

Re: So you want to modify the text of a PDF by hand (2020)

#68

Post by hackernewds »

enriquto wrote: post #17

You can do this: pdf2ps a.pdf # convert to postscript "a.ps" vim a.ps # edit postscript by hand ps2pdf a.ps # convert back to pdf Some complex pdf (with embedded javascript, animations, etc) fail to work correctly after this back and forth. Yet for "plain" documents this works alright. You can easily remove watermarks, change some words and numbers, etc. Spacing is harder to modify. Of course you need to know some po…

in vim?

Re: So you want to modify the text of a PDF by hand (2020)

#69

Post by Helmut10001 »

totetsu wrote: post #54
blincoln wrote: post #11

The PDF specification is wild. My current favourite trivia is that it supports all of Photoshop's layer blend modes for rendering overlapping elements.[1] My second-favourite is that it supports appended content that modifies earlier content, so one should always look for forensic evidence in all distinct versions represented in a given file.[2] It's also a fun example of the futility of DRM. The spec includes passwo…

Howto https://www.cyberciti.biz/faq/removing-password-from-pdf-on-...

Or:

    qpdf --decrypt
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