How do I print to PDF?

New Mac user from Windows here. I'm trying to print webpages to PDF in Firefox. When I do, they save as PDFs, but the file size is 0 bytes and the file can't be opened. The same happened with Safari using Print. I tried to install PDFwriter, which added a PDF printer, but ultimately it didn't work. What am I doing wrong? I assume, like on iPhone, that Safari has an option to save a webpage as a PDF, but I use Firefox. Surely there's a way to do this.