No active investors:

You may alter anything you want if no investors have signed up for your PAMM Fund's Offer. 

To start editing the Offer, click the Edit button under the Offers tab:

At least one active investor:

It is impossible to amend the parameters of the Offer after you have investors who have accepted them. Only the Offer name, description, and privacy are editable. 

If you have made an offer that you do not wish to utilize any longer, you can take it out of the public domain to stop new investors from signing up.