Regarding embedded fonts within PDF files, the type objects using those fonts can be easily converted to outlines from within Adobe Illustrator using the Flatten Transparency dialog box. BUT! First the PDF file must be placed into a preferably blank document using the Place command rather than opening the PDF file with the File>Open command. Also when placing the client PDF file the Link box must be checked in the Place dialog box. Once the PDF file is placed into a new document the Flatten Transparency dialog box can be used to do various things to the PDF, like outline the embedded fonts.
Art files from Canva are often just garbage quality. The SVG files Canva exports are rarely ever usable. When customers use the PDF for Print export the situation is usually a little bit better. Still, I have to round-trip the PDF material through Vector First Aid to automatically remove as much trash as possible. We're talking lots of duplicate unfilled, unpainted paths, paths that are broken open, etc. Vector First Aid dramatically cuts down the amount of repair work that still has to be done to the artwork.
It is possible for someone with real graphics production knowledge to create artwork in Canva that is more edit friendly when exported in either PDF or SVG format. However, most Canva users are rank amateurs with little if any graphics production knowledge (much less any creative talent). They don't know the difference between pixels or vectors, much less basic concepts of geometry such as aspect ratio. So they'll "design" a lot of things that won't even fit the desired space where the sign is supposed be installed. These people are just winging it. At the same time they're patting themselves on the back because they too are an "artist" now. Every child gets a gold star. The big attraction with Canva is it has a free version and the app has lots of clip art and templates.