Update README.md

Author: maartenba

README.md

@@ -28,5 +28,5 @@ There are some things to know about the project:
 
 * The project can be opened as-is in PhpStorm. No settings are included in the project yet, because these are configured when following exercises.
 * All numbered folders contain exercises that you can work on. Simply open the numbered files one by one and follow the comments in the file. Most exercises are self-contained, others build on previous exercises.
-* The PhpStorm Workshop.pptx is a slide deck which summarizes many of the items covered in exercises.
+* The PhpStorm Workshop.pptx / PhpStorm Workshop.pdf is a slide deck which summarizes many of the items covered in exercises.
 * The PhpStorm Reference Card.pdf is the PhpStorm keymap. The latest version can always be found on the [PhpStorm website](http://bit.ly/phpstorm-shortcuts).