For those who have problems, these are the steps I have taken so far:
1- Login Pledger's DLC Selection Page.
2- Choose my 4 DLC packs.
3- Press the button
A message like this appears down the page.
Quote: "4 DLC packs Have Been Assigned to your order, TGC products Please view your page to receive your keys."
4- Click on the link "TGC products"
5- You are redirected to the page "My Products"
6- At the top of the page click on the link "You can view your steam keys here"
7- You are redirected to the page "Your Steam Keys"
Here you must take the 4 keys.
8- You open the application of steam.
9. Press menu> Games> Activate a product on Steam
10- Steam opens a small window, press "next"
11- Press OK
12. Copy and paste your key, and click OK
You will receive confirmation of steam and the products selected will be automatically downloaded one by one.
About pack's content:
http://store.steampowered.com/dlc/266310/
HTH
3com
Laptop: Lenovo - Intel(R) Celeron(R) CPU 1005M @ 1.90GHz
OS: Windows 8.1 (64) - Ram: 4 gb - Hd: 283 gb - Video card: Intel(R) HD Graphics