I like that I can embed image and PDF within a markdown file via 
How can I embed Markdown within a Markdown file?
For example, I have a Markdown file, reference.md. And I have another Markdown file, journal.md. While I am writing in this journal.md, I want to have reference.md content appear in journal.md, by using . The contents of reference didn’t appear.
If the reference is a pdf file, say reference.pdf. With , the contents appears nicely.
Go to DT > Help > DEVONThink 3 Help and search for Transclusion.
However, because the help doesn’t perhaps deal as fully as it might with transclusion, what you need to do is to insert something like this in your document:
The quick response definitely help me to get the problem solved. And, the pointer to Help let me understand more about what other things I can do with Markdown in DevonThink.
I am new to both DevonThink and Markdown, less than 6 months. Still learning.