Draw on a PDF file? Well, that’s actually impossible since there’s nothing to do. Installing and using programs like LibreOffice Draw or Adobe Illustrator can help you with this.
Since they’re vector-based programs that work with outlines instead of pixels, they can create and save your drawings on a wide range of formats. Utilizing these programs (and paperspace) within the software means you won’t need more than the program itself and a type of editing software–which is just as it should be in regards to any design process/skill set 😉