How can one use system dictionary ^+⌘+D in .pdf's opened in Safari 6 (using Acrobat Reader)? Is perhaps Adobe Reader at fault (i.e. does the dictionary work with Safari's default .pdf reader)?
The program that draws the text needs to use one of Apple's standard SDK for drawing text for the shortcut dictionary to work. Since safari is handing the PDF over to Adobe to render - they apparently are not using a standard text field but have implemented their own code/class to do the drawing.
This is very common for web browsers like Chrome and other programs that desire to avoid being a Mac program and instead be more cross platform.
In your case, simply ditching the Acrobat plug in will restore the PDF handling using the native tools and your dictionary shortcuts will work again.
Simply delete the
In my testing, the ⌃⌘D shortcut doesn't work in Preview or PDFs within Safari. However selecting the word, and using the Look Up in Dictionary item from the context (right-click) menu does work as expected (it displays the yellow highlighting and popup, not the full Dictionary app).
I'm not sure why the shortcut doesn't work, but it's a decent work around at least.