“Kindle”: is not just for reading Kindle books. You can read your files in Kindle as well. You need to manually convert the files into Kindle format though.
That’s not an optimal experience. But, well, it’s better than nothing.
There are official and 3rd-party ways for doing so. The official is offered by Amazon. You just need to email the document to your Kindle email and that’s it! The official converter supports most comment document: PDF, HTML, JPEG, PNG, DOC, etc. You can refer to Amazon’s support page for instructions – Transferring Documents and Files to Kindle 2.
Result of the official conversion is fine for simple PDF document. When it gets to the Apple’s documentation, it’s far from perfect. But it’s should be fairly OK for casual reading. You can check the sample below:
You can see some words are cramped together (the top few sentences). Weird…