Can Kindle read PDF? Yes, but not scanned ones. Here is the fix

Two kinds of PDF, two different results

Whether a PDF works on Kindle depends on what is inside it, not on the file name. A PDF exported from Word, a publisher or a web page contains real text. A PDF from a scanner, a phone app or a library such as the Internet Archive often contains only an image of each page.

How to tell which one you have: open the PDF on a computer and try to select a single sentence. If you can, it has text. If the whole page highlights as one block, or nothing highlights, it is a scan. When we built a PDF from the scanned pages of an 1872 book, pdftotext found exactly zero words in it.

If your PDF has text: use Send to Kindle

1. Go to Amazon's Send to Kindle page in a browser, or use the Send to Kindle app on your computer or phone.
2. Add the PDF. Amazon's help page lists PDF and EPUB among the supported file types.
3. If you are offered the option to convert the PDF to Kindle format, accept it. Without conversion the file stays a fixed PDF.
4. Open the book on your Kindle and check a few pages. Columns, tables and footnotes often come out in the wrong order.

If the converted layout is poor, converting the PDF to EPUB yourself and sending the EPUB usually gives a cleaner result, because EPUB is the format Send to Kindle handles best.

If your PDF is a scan: OCR first, then send

A scan has to be read before it can reflow. Plain OCR is not enough on its own: it returns the words, but it also keeps every page number and running head and has no idea where chapters begin. In our test, the Internet Archive's OCR-based EPUB of a 214-page book had an empty table of contents and only 88.5% of its words belonged to the book.

1. Upload the scanned PDF, or a folder of page photos, to upub and choose your Kindle model, for example Kindle Paperwhite or Kindle Scribe.
2. upub reads every page with an AI model, removes page numbers and running heads, joins paragraphs across pages and builds a table of contents.
3. Download the EPUB and send it with Send to Kindle. Kindle converts EPUB to its own format, and the font size slider now works.

On the same 214-page scan, upub's EPUB matched 99.2% of the proofread text, carried 39 table-of-contents entries and passed EPUBCheck with zero errors. You can download that file below and send it to your own Kindle to see the difference.

Why not just use Calibre or k2pdfopt?

Both are good free tools, but neither turns a scan into text. Calibre has no OCR: on our test scan it recovered 18 words of the book. k2pdfopt re-cuts the page images so they fit a 6-inch screen, which helps, but the result is still a PDF of pictures. Our tool comparison has the numbers.

Kindle Scribe and large screens

On a 10.2-inch Kindle Scribe a scanned PDF is much easier to read as it is, and you can write on it. Convert it when you want to change the font size, read on a smaller Kindle or the Kindle app on your phone, or use the dictionary and search.