1
Download and install the Kindle app for Mac.
By using Send to Kindle, you agree to the terms here.
Supported File Types:
PDF, DOC, DOCX, TXT, RTF, HTM, HTML, PNG, GIF, JPG, JPEG, BMP, EPUB
2
Go to System Settings > Privacy & Security > Extensions > Sharing.
3
Check the box to select "Send to Kindle".
4
In Finder, right-click on the file you want to send, choose Share and Send to Kindle.