If you choose to enter HTML code, Pdfcrowd translates the code into PDF for you, and there's a WSISWYG editor available for making tweaks. After you set your options, hit the button to convert ...

Click the PDF link in the Upload Complete window to open the PDF in a window. Click the "File" tab on the PDF ribbon, and then select "Embed This PDF File" to open the window with the HTML code.

The vulnerability impacts TCPDF, one of the "big three" PHP libraries --together with mPDF and FPDF-- for converting HTML code to PDF docs or assembling PDF files on the fly.