Viewing PDFs with another font

[Font]

Suppose a PDF has embedded font. Could it still be viewed with another font? If it could be done then is there a way to test it on a computer first? Would the PDF have to be converted to another format? Does Calibre software allow converting a PDF file to another format? Basically what's easiest to change the PDF fonts? Supposing the PDF has more than 1 embedded font, then could it still be converted?

[fjtorres]

PDf files are not ebooks but rather digital paper. As such the formatting is hardwired and controlled solely by the publisher.

As you surmissed, the only way to control display of a pdf file is to try to extract the content from the file and convert it to an editable format. If the PDF is DRM free and not too complicated (mostly text) Calibre can do a decent job. Mobipocket Creator (free at Mobipocket.com--make sure to install it as the Professional edition) does a somewhat better job (it outputs Mobi format but the conversion folder also contains a generally very nice HTML rendition).
If the pdf is very complicated (columns, tables, text boxes, graphics, etc) the only real option is a professional converter like Abbey FineReader or Nuance OmniScan that "prints" the PDF to memory and then OCR that virtual page to create an editable document file that replicates the pdf formatting.

If it sounds like a lot of trouble, understand that PDF was designed to *prevent* you from freely accessing the content in edittable/re-formatable form and does a very good job of it.

[owl123]

Actually you might try changing PDF's font with... a hex editor. The font can't differ much though or the text will look all messed up.

[rkomar]

Originally Posted by owl123

Actually you might try changing PDF's font with... a hex editor. The font can't differ much though or the text will look all messed up.

Yeah, the kerning (i.e. positioning) of each character is done according to the font used when the PDF was created. New font characters get placed in exactly the same positions, even if they are shaped differently. I remember trying to read PDF files created by Acrobat on an open-source reader called xpdf about 10 years ago, and the text looked horrible because the Adobe fonts weren't freely available back then. When Adobe released their fonts, the rendering in xpdf improved dramatically for those files.

As fjtorres mentioned, creating a new PDF file is best so that the words are kerned using the new font.

[paaThaka]

Originally Posted by fjtorres

PDf files are not ebooks but rather digital paper. As such the formatting is hardwired and controlled solely by the publisher.

Postscript, which is the decription language used inside PDF files, is turing complete.

Many text PDFs also contain the text as a separate content and the font as separate. Those that have fonts converted to paths, do not have text content as separate from the typeface.

So yes, the font is changeable if one uses a postscript interpreting system like ghostscript or similar.

This is also how reflow in PDFs works, changing the values in the postscript description.

So, for many if not mosts files the font is theoretically changeable as long as the PDF container is not protected and the fonts have not been converted to paths.

As for the PocketBook, I do not think it currently offers this functionality.