Override TinyMCE markup when a file is dragged in

I would like to override the markup generated when a file (pdf in this case) is dropped into the TinyMCE editor. as I would like to add some extra properties to the markup which are present on the file itself.

the PdfFile type is a expandsion on the MediaData class, with things like filesize and title.

currently it generates this:

<p><a title="some-pdf.pdf" href="some-pdf.pdf">some pdf</a></p>

I would like something more like:

<p><a title="pdfTitle" href="some-pdf.pdf" data-some-attribute="pdfTitle">some pdf (PdfFileSize)</a></p>

I am unsure as to

1. how to amend the template which is used by TinyMCE - if that is how it works
2. how to grab the extra properties in this instance to insert into the template

I know when the file is dropped into the editor, it calls an ajax method, which returns the markup /EPiServer/cms/Stores/contentdata/contentId_workID but that is about it

thanks