The answer depends on the type of XML you want to convert PDF. If it is a preexisting XML schema and you want to say a form then you can look at XSL:FO which using XSL style sheets to convert from data XML to a formatted PDF. It's a complex specialized skill however.
If you can create an XML description of the page layout, placing data from Switch metadata, datasets and job assets then you could use Apago PDF Constructor. We have implemented many flows that build impositions, job-tickets, variable data documents, fillable forms with digital signatures, multi-media PDF, etc all inside of Switch.
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sales@apago.com for more information.