Which Kindle files can become a PDF, and which cannot
Kindle books come in several formats that look alike from the outside. MOBI is the older one, still common for books from small publishers and free libraries; AZW3, also called KF8, is the newer one; and AZW is usually a store purchase. Whether a file converts depends far more on where it came from than on its extension.
Updated
Which tool you need
A MOBI from a free library or a small publisher
This is the case the tool reads best: the text in order, with headings, lists, emphasis and pictures, and a new page wherever the book starts one.
An AZW3 file
Try it, and read through the preview before saving. The text comes out in order, but formatting that relies on the newer format's styling can come out plainer.
A book bought from the Kindle store
It will be refused. Store purchases carry DRM, and the tool reports that instead of producing pages of noise.
The same book is also sold as an EPUB
EPUB to PDF keeps more of a book's structure, such as its tables, so it is the better start when you have the choice.
What an older Kindle file holds
A MOBI book is a small database of compressed text records with its pictures stored after them. The text is a simplified HTML, which is why headings, emphasis and lists survive the conversion while fonts and spacing do not.
Some files are packed with a scheme called HUFF/CDIC, used mainly by older dictionary-style books. That one cannot be read yet, and the tool names it rather than failing silently.
Newer KF8 files, and files that carry both formats
An AZW3 book, also called KF8, stores its HTML in pieces: skeletons with fragments slotted into them. Read in order, those give the words in the right sequence, but the style sheets and drawings stored after the text are not used, and they are where a newer book's layout comes from.
Some Kindle files carry both formats at once, an older MOBI copy followed by a KF8 one. When a file does, the older copy is the one read, so it converts as fully as any MOBI.
Plain Palm books
Before MOBI there was PalmDOC, the plain book format of Palm handhelds, usually found as a .pdb file, and it is read too. It has no markup at all, so the PDF is its text line by line, with no headings, emphasis or pictures, titled with the name stored inside the file.
What to know before you start
- Kindle store purchases cannot be opened, because of their DRM.
- AZW3 formatting is simplified, though the text keeps its order.
- Writing in a script the chosen Fonts level leaves out shows up as a replacement mark.
- A plain PalmDOC book comes out as its text alone.