I would like to call paid fonts via pub folder. I create the specific font folder in pub i.e
pub/static/frontend/Mageplaza/ultimate/en_US/fonts
and linked it my custom.css file font family is not working.
You are doing in a wrong way, As per magento standards, do not upload any files directly to the pub/ folder.
if you want to add font family upload the File under
web/css/fonts
in your custom theme or Module View folder. To call the font face, create/modify custom.css in following path,
web/css/custom.css