ePub->pdf conversion doesn't allow to add watermark with third-party pdf editor

[EbokJunkie]

Seven years back in April 2016 this thread discussed the problem of adding background color to pdf produced by epub conversion. Back then I advised to try free PDFill tools to add jpeg or bmp texture as all-page watermark to obtain desired background color. My guess is back then in 2016 most people used Windows 8.1 and PDFill tools worked perfectly well for Calibre PDF output.

Today I noticed that under Windows 10 even latest PDFill Editor fails to add watermark as proper background.

OK, I also had latest edition of Adobe Acrobat and decided to find out what was going on. First I verified that both Adobe Acrobat and PDFill Editor were perfectly able to add all-page jpeg texture as watermark to my math pdf books.
However, Calibre generated PDF file opposed to Acrobat/PDFill Editor attempts to add usable all-page background watermark.

See attached screen captures:
First one demonstrates watermark behind page created in PDFill Editor in year 2023 (Adobe Acrobat watermark looks similar).
I intentionally stretched watermark to cover both text and page margins.
Note that watermark is visible ONLY across all four margins but is fully hidden away across the page text.
Second capture demonstrates successful all-page watermark added to Calibre created pdf in year 2015.

Evidently the text area above the 2023 watermark is 100% opaque and hides almost whole watermark.
Also note that Adobe Acrobat simply refuses to change background color for Calibre generated PDF.

My question to Kovid: Is there any hope to return to Calibre generated PDF
its lost since Windows 8 ability to accept proper watermark/background color from third-party PDF editors under Windows 10/11?

P.S. If needed, I have pdf file of Lewis Carrol, Through the Looking Glass created by ePub->pdf in year 2015 – it still allows today to add good all-page watermark under Windows 10

[kovidgoyal]

No there isnt. Originally calibre used to generate the PDF itself by implementing a drawing backed for Qt webkit. Qt Webkit was discontinued. Nowadays calibre uses Qt Webengine to draw the PDF, your issues will come from that. And no there is no hope of that changing.

[EbokJunkie]

Thank you, now I understand what happened, Qt Webkit was deprecated somewhere about 2016. Kovid, what Calibre version was the latest using Qt Webkit for PDF? Maybe it will run on Windows 10?

[kovidgoyal]

3.48 IIRC

[BetterRed]

Originally Posted by EbokJunkie

Kovid, what Calibre version was the latest using Qt Webkit for PDF? Maybe it will run on Windows 10?

Originally Posted by kovidgoyal

3.48 IIRC

Can't speak to epub->pdf conversion specifically, but 3.48 runs on Windows 10 just fine for me, including the viewer.

BR

[Doitsu]

@EbokJunkie if you don't mind using a command line tool, you could add watermarks with cpdf.

You only need a .pdf file of the watermark image that you want to use. The command is:

cpdf -stamp-under watermark.pdf -scale-stamp-to-fit in.pdf -o out.pdf

[EbokJunkie]

Thanks Kovid, BetterRed,

Really, 3.48 does everything for ePub->pdf conversion on Windows 10 and output PDF is perfectly modifiable with PDFill Editor. BTW, conversion is faster with QtWebKit.

[EbokJunkie]

Originally Posted by Doitsu

@EbokJunkie if you don't mind using a command line tool, you could add watermarks with cpdf.

You only need a .pdf file of the watermark image that you want to use. The command is:

cpdf -stamp-under watermark.pdf -scale-stamp-to-fit in.pdf -o out.pdf

Thank you, will try cpdf for sure.

[EbokJunkie]

One observation regarding adding watermarks:
ePub->PDF book has 568 pages and size ~3 MB.
jpeg file containing watermark is~ 19KB.
Watermarked book sizes with all-page watermark added:
after Adobe Acrobat: 13 MB
after PDFill Pdf Editor: 3.1 MB
Question: What PDFill Pdf Editor knows about watermarking that Adobe doesn't know?