I made a business card in Canva and dowloaded the pdf for print. The printing place requested that I convert to CMYK, convert/embed the text and include a 3mm bleed with crop marks
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
Buy or get a free trial of Serif PagePlus X9. It's an intuitive graphics and text composing program that covers professional (=CMYK) printing needs, too. It's purposed to be a low cost alternative to Adobe InDesign and that it really is. PagePlus must be paid only once. The price is less than Adobe bills for one month InDesign usage.
Import your design into PagePlus, add the required reserve space, select printing markings to be inserted, choose output as CMYK and select all fonts to be converted to outline curves (=avoid font piracy issues).
If a printing house really wants you to bring your money to them, they very likely give to you an exact list of required settings.
i guess first instance would be the vendor or printing place is facing problem as he or she might open the pdf using either of adobe software so the missing font error and please check the colour properties if you are using pantone or RGB value. The second instance, when you might have designed the artwork you might have forgot to put the crop. I have attached the reference image for your understanding.
I have not used that program and probably never will. Those kind of design programs are a bit useless. They are targeted at home users to be printed in your home. A CMYK version has no sense if the output is digital. If you need let's say 100 cards, it will be digital.
Regarding the bleed, you need to actually make the design 6mm bigger.
So choose for example a different size to begin with.