Unless you restrict it, a PDF is always editable. You can save your DOCs as PDFs. Anyone with a PDF editor like Soda PDF can then edit the content. If you want a form, I’d just use Google Forms.
When you click “Save as PDF”, it saves it as a.DOCx file. You can download those via DOCX Browser. When a form is saved as PDF, it is saved immediately to the “Save to PDF” panel. You can go to File ▸ Save as PDF, and click that to load a .DOC file. Once you have downloaded the PDF, you can edit it, but it will look a little strange. PDFs are great for sharing with other people. You can print a PDF from the website. I don't really see a use for this. It's a lot more convenient to use the web's Print to PDF function. Even when you have saved a PDF, it doesn't look in the same way. You can go to File ▸ Print To PDF, and then pick a file you want to print. I like how you can choose a file, and.