Update readme

- notation fix, 'hyphen' --> 'colon'
- markdown fix, use double asterisk for "strong emphasis" instead of headers

scripts/pdf/README.md

@@ -17,13 +17,13 @@ This directory contains the script and related resources to generate a PDF copy
 
 ## Requirements
 
-The PDF is generated by first converting the markdown files to HTML, and then rendering those HTML files as PDF. It depends on the following libraries-
+The PDF is generated by first converting the markdown files to HTML, and then rendering those HTML files as PDF. It depends on the following libraries:
 
-#### Python-Markdown
+**Python-Markdown**
 
     pip3 install markdown
     
-#### WeasyPrint
+**WeasyPrint**
 
     pip3 install WeasyPrint