When you are organizing contests then you do have to send prizes to the winners. It is a great idea to offer prizes as digital content. You can contact a company which is based in your blog niche and then can ask them you can wish to offer your readers prizes for the contest. You can discuss with them the options, say if they provide you with 3-4 free licenses of their product you can mention in the contest about their company. This will be a win win situation for both you and that particular company in question. They will get the publicity and you will get giveaways for free. Even you can pay half of the amount of the licenses. The way how you handle the deal with the company is totally up to you. The bottom line is that you can give prizes to the winners in the form of digital content.
When you have a deal with the company, then you can use this WordPress plugin to create a secret code for that particular product. The target page can only be accessed provided someone types in the code. You can then send the secret code to the winners of the contest. They can type the code in and can access the files and other materials.