The tracking link automatically updates with a hashed version of the parameters in the original tracking link. Boom, ka-bang, you can now see your PDF's Pageviews, Unique Pageviews, Avg.
Also, remember that many services provide 14 day free trial so you can check if it fits your needs before spending any money. Once you've found a domain you like, you'll need to register it. While URL shorteners have had some incredible usage tied to the growth (and constraints) of Twitter, I question their sustainability as a business. It creates short URLs and also keeps a track of All clicks and gives superb statistics. Instead of posting the "pretty" URL, you can shorten it by removing the "www." and using the post ID in the URL (e.g. "?p=1204").
In order to form the key, a hash function can be made, or a random number generated so that key sequence is not predictable. If you copy and paste this script exactly as it appears here, your outbound clicks will appear in your Analytics Events reports with a Category of "outbound" and an Action of "click". (In the snippet, these are shown in bold.) You can use these values, or change them and define your own values. A shorthand link is associated with the registered URL. This way they can use shortened URLs but still give people confidence about where the link will lead.
See if you are using Classic Analytics (ga.js) or Universal Analytics (analytics.js).