Everything here is free, runs in your browser, and asks for nothing — no account, no watermark, no limit. The first four are the same editor opened onto a different document, so anything you write in one can become another without typing it twice.
One job usually needs more than one document. You quote for the work, you invoice for it when it is done, and you receipt the payment when it arrives. Those are three documents saying much the same thing, and typing them out three times is how numbers stop matching.
So the first four tools are one editor with the document type already set. Open a quotation, and when the customer says yes, press New from this and switch it to an invoice — every line, both parties, the tax setup and your payment details come across unchanged. Do the same again for the receipt. The three documents then agree with each other, which is the only reason anyone keeps them.
Nothing is stored anywhere, so a document survives the tab being closed only as a draft file you download. Drop that file back on the page whenever you want to carry on, or open it next month and start the next one from it.
These notes are general guidance, not tax advice. Tax treatment depends on your registration status and the nature of the supply — confirm anything you are unsure about with your accountant.