Originally Posted by Starson17
It's likely this is a text-based pdf. They convert OK in Calibre.
At this point, Calibre can't handle multiple column pdfs. Conversion will fail if it's a text-based multi-column pdf. If it's an image based pdf, conversion will succeed, but you'll only get images of pages full of text, so no text size management is possible. I can't be sure, but I suspect you are confused between image based pdfs (images of pages having text that look like text but are really pictures of text) and text-based pdfs. In the former, your pdf is just pictures. Only the latter has text that can be controlled with text size options.
When pdfs have both true text and graphics, conversion will work, but image placement relative to the text is often lost.
I suspect that this has nothing to do with whether the pdfs have graphics.
I don't have a kindle, but I have the same issues with pdfs. Some are scanned page images of text, and some are true text. Only the latter type can be converted to other formats with any success.
OCR the text images to convert to true text, then convert that.
As to your questions about images on the kindle, I can't help you at all.
Thank you for your responses. I think I understand all of the answers and this is really helpful.
I'm intelligent but not specifically computer-oriented, so allow me to throw out my plan of action and let me know if this is the wrong course.
I have a rather large, mixed collection of pdfs (should be variations of image-based and text-based) that need converted to .mobi files. I'm going to use Acrobat's OCR option and do a multiple file conversion to first make them all text-based files. Then I will put these new files in calibre and convert to .mobi and hope for the best. Is this the best course of action? Should I change any of the layout or output options to get the best results?