I am in the Filling and sign area to type a document, and I want to change the font and put some things in bold. How do I do that?
You can change the font for a PDF form (Acroform type PDF forms as opposed to LiveCycle forms) if you are using Adobe Acrobat and the PDF file is not locked against modifying the PDF file. This cannot be done in Adobe Reader.
You would need to modify the form field(s) in question, changing the field definition to use an embeddable font and also set the definition to allow for the form filler to switch to italic, bold, etc. from within the forms field.