Epub to Pdf conversion bloating file size 2 to 5 times.

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I'd like to find out why some epub documents will convert to the pdf format using the Calibre book conversion tool, with an output file size much larger than the the input document.

It's common for pdf output result's to be either 2 or 5 times the size of the input epub document, but I've also got one example where the pdf output remains the same size as the epub input, and all conversion settings where more or less the same.

If you'd need to see content examples to help troubleshoot, is there an approved method of sharing copyrighted material on this site, such as over direct message?

For reference: I'm using a 7.17 'portable' instance of Calibre (not too old) but don't see how that'd be the most likely cause, unless pdf file bloat was a known bug since addressed.

[kovidgoyal]

Because PDF files have inferior compression and depending on the font being used the fonts can end up being embedded multiple times. And no this is not going to change.

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Hi Kovid,

thankyou for at least confirming it's a known problem. I'd guessed it could be due to repeated font embedding also after monitoring the conversion process.

Anyway, thankyou for creating this brilliant program.

Best wishes,

Nick.

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I have an epub with images which I have linked the images by url to a server folder. But if I convert the epub to PDF the image does not display it shows linked images as a blank as shown in attachment.

[kovidgoyal]

Yes conversion is not going to fetch remote resources and rely on network connections. Use the edit book function in calibre which has an external links tool that will automatically download external resources before converting.