All the PDF editors I have tried (Adobe, Foxit, PDF XChange Editor, all work fine for reading documents. Some give you a few decent features, but none I have found let you restrict the document from being edited. E.g. when you send the PDF to someone and they try edit it or open it in word it won’t work
PDFCreator (Windows Only): PDFCreator is a free tool that allows you to create PDF files from nearly any Windows application. With it, you can encrypt your PDF files and protect them from being opened or printed, and you can also restrict access to your PDFs by setting passwords.
QPDF: This is a command-line program that does structural, content-preserving transformations on PDF files. It can encrypt and decrypt PDF files, and it can also set various access limitations.
LibreOffice Draw: LibreOffice is a free and open source office suite. The Draw module can open and edit PDF files, and it also allows you to set a password to open the document, as well as to restrict editing and printing.
Please remember that even though these tools can restrict editing, they may not be 100% foolproof against all PDF editing tools or techniques.