This is what the @audience attribute is for in DITA:
<p audience="enduser">Enjoy this training course. After going through it you will be a rock star.</p>
<p audience="admin">This certified training course is for IT-Professionals only.</p>
You just apply your self-definied attribute values. For HTML5 output you define the values and then users of the output can "filter" the content on their own with checkboxes, or you create multiple outputs. As uch filtering is not there in PDF, for PDF you would just create multiple PDFs.
Personally, I prefer this way of attribute-based filtering over conditional text in XML projects.
Thank you everyone for your input on this question. Much appreciated.
Having looked at the the Elements available in just a DITA topic, none of our content writers/consultants won't have a clue what elements to use. They will find it endlessly frustrating and just end up creating documents in MS Word because it's easier. It also doesn't enforce the restrictions we have in our Corporate Style Guide, e.g. bulleted and numbered lists cannot be more than 3 levels deep; no more than 6 heading levels are allowed under a topic.
In contrast, our custom EDD has elements that our content writers/consultants can relate to, e.g. Heading, Paragraph, BulletList, NumberedList, Screenshot, InlineImage, Notes, FieldList, etc.
I can see the benefit of going with DITA if you don't have any sort of document structure in placed, or if you're in an industry where there is an established structure that you have to adhere to. Neither is the case in our organisation. We're also fortunate that our Style Guide for training documentation is very clear on the formatting/layout of said documentation. The comment raised by @Stefan Gentz about wanting additional elements or using elements in an unsupported context just aren't ones entertained. The structure is defined for a reason - revise the context in which you want to add the content to conform to the structure.
I'm in favour of using establishes standards, provided they are appropriate. In our case, DITA as a standard won't work for our organisation. As @frameexpert mentioned, creating a custom Structured Application might we the better solution for us.
Thanks,
Quintin