You've got a long PDF you want to read on your Kindle — a textbook, a report, a long-form article collection. You send it via Send to Kindle and it shows up as a tiny, unreadable page-sized PDF. The Kindle isn't designed for that.
EPUB is what Kindle wants.
Why PDF reads badly on Kindle
PDFs have fixed page dimensions. Kindle reflows text to fit the screen size and your chosen font size. Two formats with opposite philosophies. The Kindle shows PDFs as-is, shrinking the whole page to fit — text becomes tiny, you have to zoom and pan.
EPUB reflows properly
EPUB is the standard ebook format — text reflows to any screen, font size adjusts, chapters are navigable. Kindles accept EPUB via Send to Kindle (since 2022, Amazon dropped its proprietary requirement for AZW3/MOBI).
Convert PDF to EPUB via Flint's convert hub, then send to your Kindle via the Send to Kindle app or by email.
Conversion caveats
Text-based PDFs convert to clean EPUB. Scanned PDFs need OCR first; the result is usable but proofread the OCR output before reading.
Two-column journal articles convert better when the layout is recognised. Sometimes you get one merged column of perfectly readable text; sometimes you need to re-flow paragraphs manually. Most modern non-fiction PDFs come across well.
Images, footnotes and the rest
Images carry across as embedded images. Footnotes usually arrive at the end of each chapter rather than at the bottom of pages (because pages don't really exist in EPUB). Tables flow as tables; very wide tables may need adjustment. Equations come across as images, not editable maths.
FAQ
Can I send EPUB directly to Kindle?
Yes — since 2022, Send to Kindle accepts EPUB. The Kindle converts it internally to KF8 for display.
What about MOBI?
Amazon's deprecating MOBI in favour of newer formats. EPUB is the better target.
Will my notes carry across?
PDF annotations don't transfer to the EPUB. Any highlighting you do on the Kindle is stored there independently.
Image-heavy PDFs?
Carry over fine, though large images may look chunky on smaller Kindles. Modern Kindle Scribe and Oasis handle them well.
Readable on a Kindle finally. Convert your PDF to EPUB and send to your Kindle.