Question: Is there any function that can print a symlink's full path in `dired` mode? Alternatively is there any function that can print an arbitrary buffers' full path?

Answer: 
Since my comment fixed the problem, I'm posting it as an answer here.

It seems that you don't have any executable called markdown in your PATH. Installing daringfireball.net/projects/markdown (preferably from some package manager like homebrew) should fix it.
Installing `markdown` with `brew` didn't solve it for me. I had to add the following command to my **Emacs config** file:

```
(custom-set-variables
 '(markdown-command "/usr/local/bin/markdown"))

```

Also, later on I changed:

```
"/usr/local/bin/markdown"

```

to:

```
"/usr/local/bin/pandoc"

```

Because for some reason the preview and exported files were looking nicer (maybe it's just me), I would suggest giving it a try.