You can file an amendment to increase the authorized number of shares in your articles of corporation, which you should have filed in the state of Idaho. If you have lost your copy of your articles, they are on file with the state and can be ordered.
There is no legal restriction on how much you charge for your shares so unless the issue is you want to sell in smaller denominations so that you raise more money selling a smaller stake of your company, such an amendment should not be necessary. Also remember in terms of determining voting strength that voting is determined in respect of shares outstanding, not shares authorized. So, for instance if you have 20,000 shares authorized and you've issued yourself 5,000 shares and you then increase your authorized shares to 40,000 and sell 10,000 shares -- you haven't sold 25% of your company, what you've now down is convert yourself from a 100% owner (5,000/5,000) to a 33% owner (5,000/15,000).
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