You can apply your signature using Acrobat, or any number of other programs that edit PDF files. Some of the methods are cheaper than an ACI signature, and some are more expensive, but all are more flexible in their use. I highly recommend spending the money for a digital ID that validates your work. It is far more secure than anything offered by any forms vendor.
If your issue is just with the cost, get over it and spend the money. Do be sure the file is sent only to you, and not your supervisor. Never share your password with anyone. Change your password before you sign your first report, or load your signature on a machine you do not own.