Just compose a new email message, attach document(s) that have to be converted into PDF and send the email to firstname.lastname@example.org. The PDF file(s) should arrive in your inbox the next moment.
See alternative: Convert Files and Documents by Email
The big advantage is that Koolwire PDF converter requires no software installation and, unlike Google Docs or PDFOnline, you don't have to upload documents to any webserver in order to print them as PDF - just send them across as email attachments. PDF creation couldn't be simpler.
Best of all, you can attach multiple documents / images to the same email message and Koolwire will batch convert them into PDF. Don't think any free PDF writer software offers such a convenient option to create multiple PDFs in one go.