By default you are only allowed to upload image based files into the WYSIWYG editor built into Magento. If you need the ability to upload PDF files here is how.
- Navigate to: app/code/core/Mage/Cms/etc/config.xmlAround line 110 onwards you will see:
<allowed> <jpg>1</jpg> <jpeg>1</jpeg> <png>1</png> <gif>1</gif> </allowed>
- Add in the line:
where needed and upload your file.
- Clean your cache. System -> Cache Management