To transfer PDF documents to a Kindle, you can use the Send to Kindle service, which allows you to send documents to your Kindle library at no additional cost. You can upload documents through the web, an authorized email address, or the Kindle app for iOS and Android devices. To send a PDF to your Kindle, you can email it to your Kindle's email address, which you can find in your Kindle's settings. Once you've sent the email, the PDF will be added to your Kindle library, and you can access it on your Kindle device or in the Kindle app.
Alternatively, you can transfer PDFs to your Kindle by connecting it to your computer via USB and dragging the PDF file into the Documents folder on your Kindle. You can also use a third-party application such as Calibre to convert your PDFs to a format that can be read on your Kindle. By following these steps, you can easily transfer your PDF documents to your Kindle and read them on the go.