Since yesterday a large number of people cannot render fonts correctly.
Looking into it, everyone with the issue was linking to fonts hosted in Google Drive or DropBox.
Example code below:
src: url('https://www.dropbox.com/s/lwzc1rcgziyyl9e/trade-gothic-lt-std-5914a7ed793fe.ttf?dl=1') format('truetype');
The link to the font file resolves fine and works everywhere else, however PDFCrowd seems to time out on it.
As noted, this worked fine until yesterday.