Best way to display page full of links?

I have a page that looks like below.

I shrunk it in dimensions to give a broad idea of the page. So it has categories and under them there are links. What would be some of the options in terms of designing this page? I was thinking when user clicks on any link, If the link is a pdf, I could load it on the right side and show preview like below:

I am not sure if it's a good idea in terms of user experience. A lot of these links are either word or pdf files to be downloaded or viewed for the user. Some will take user to an another website.