There is a lot of confusion about what PDF protection actually achieves. It is worth understanding before you rely on it.
A password that is required to open the file is real protection, because the contents are encrypted. Anyone without it sees nothing. That is genuinely useful when emailing something sensitive.
Restrictions on editing or printing within a PDF are a different thing and much weaker. They are honoured by well behaved readers and ignored by others, and stripping them is trivial for anyone who wants to. Treat them as a polite request rather than a lock.
Sending the password in the same email as the document defeats the whole exercise. Use a different channel, a message or a phone call, otherwise anyone reading that mailbox has both halves.
The password in this tool controls who can open the document. It does not set rules about editing, so once someone has opened the file with the password they can still use a PDF editor on it. Do not rely on it alone to stop changes.
A more effective step is to send a version where the pages are pictures. Converting the pages to images and building a PDF from them with Image to PDF, or compressing the document, leaves no text to change in an ordinary editor. A watermark adds a visible reminder of whose document it is. None of this is foolproof, and a determined person with the right tools can still redraw a page.
A strong password on a properly encrypted PDF is genuinely hard to break. A short or obvious one is not. The password you choose does most of the work.
No. It makes copies traceable and discourages casual reuse, which is a different and more realistic goal.
No, the encryption happens on your own device, which is rather the point for a document worth protecting.
No. It only controls opening. This tool does not add editing restrictions, so a person who has the password can still change the document.