This will add to your visibility. Add a note recommending visitor's to subscribe to your publication or check out your home page. Trade links with other publisher's. Send an email to other publisher's and see if you can work out a deal. Offer Free Contests for new subscribers.
People love the opportunity to get something for nothing.
Offer the opportunity for your visitors to win something of value for subscribing to your publication such as free advertising space, a free demo of your product or service, etc. Organize a joint venture with other publishers. Offer other publishers the opportunity to add to there subscriber base by joining you in a contest. Then each publisher advertises this contest in their own publication. You will find that subscribers to the other 4 publications will be joining yours for the ability to participate in the contest.