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At least TexLive creates PDFs by default in version 1.5. Why this particular version?

This question has been asked before in a comment and didn't receive the attention it deserves. (duh!)

This site alone has multiple questions concerning the problem of includegraphics-ing a PDF of a higher version. From the answers, this rather simple problem magically disappears if one changes the version of the output PDF to the appropriate version ... without any side effects.

There are three things about PDF 1.6 which look particularly nice to have:

  1. Embed OTF fonts; no converting required anymore
  2. AES encryption of PDFs; 1.5 only supports RC4
  3. Use the PDF as file container

Number 3 requires a little more explanation. I am thinking along the lines of assignments, collaboration and archiving. With this feature we can have PDFs which carry with them any of the following:

  • all source files of used graphics,
  • raw data for statistics,
  • complete, unabridged and ugly source code files and runnable/parsable scripts
  • the solutions to a test as a separate PDF
  • the entire workdir of *TeX while creating the PDF
  • the actual source PDF, or HTML page if need be, in the bibliography (where applicable)

Yes, I am very intrigued by 3.

With PDF 1.7 we could also store default printer settings with the PDF. This is not that big of a deal, but would smooth out some more ruffles that occur occasionally.

I guess most of the things on my wishlist don't exist out of the box, but currently I still have to wonder if there is a particular reason to stick to version 1.5, especially as it is as easy as setting a single value to move to a more recent version. What are the side effects of moving to PDF 1.7? Are there negative side effects?

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    I think the main issue is that not all of the tools in texlive that consume pdf are known to work with higher versions, so by default better to generate a safe pdf that is known to render in all viewers on all platforms, etc. Mar 29, 2016 at 11:46
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    Embedded File Streams exist since PDF v1.3 (section 3.10.3 of PDF Reference, second edition, July 2000). Look at attachfile package... Mar 29, 2016 at 12:21
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    Simply because this hasn't been revisited since TeXLive 2010 (when the default was raised to 1.5). Apr 2, 2016 at 17:10
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    1.5 was chosen as at the time that was the version best supported but (a) it's only a default, you can change it site-wide or per document (b) it only affects the number written in the header it has no effect on the pdf written, so if you use a pdf 1.7 feature without changing the \pdfminorversion probably only pdf validators will complain, the features still get used in the pdf file Aug 7, 2022 at 16:06
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    (b) is extremely helpful information. Thank you!
    – Bananguin
    Aug 9, 2022 at 8:57

2 Answers 2

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The reason why TexLive creates PDFs by default in version 1.5 is simply because that is the default version set by the PDF specification. PDF 1.5 was first published in 2003, and as such, it has been around for a while, making it a well-established standard that is widely supported by PDF readers and other software.

Regarding the advantages of more recent PDF versions, as mentioned in the question, PDF 1.6 introduced the ability to embed OpenType fonts without the need for conversion, as well as stronger AES encryption for PDF files. PDF 1.7 added some additional features, such as the ability to store default printer settings with the PDF file.

In terms of side effects of moving to a more recent PDF version, the main issue to consider is backward compatibility. PDF readers and other software may not support the latest version of the PDF specification, which means that users may not be able to open or view the file if it is saved in a more recent version. In general, however, the newer versions of the PDF specification are designed to be backwards-compatible with older versions, so this should not be a major issue.

In summary, while there are some advantages to using more recent versions of the PDF specification, the default version (PDF 1.5) is widely supported and generally provides adequate functionality for most use cases. If backward compatibility is a concern, it may be best to stick with the default version, but otherwise, it is generally safe to use a more recent version of the PDF specification.

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If you are a writer who uses a print-on-demand service, to publish a book on paper (not Ebook), then you may be limited to PDF 1.3 or 1.4. Even in the year 2023. No problem, TeX does it when requested. Of course, then you will not be able to use features that appeared in 1.5 or later.

Why the limitation? The older PDF versions are closer to "paper" than are the newer versions, which are closer to "badly formatted web page".

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