If the Petitioner contact associated with an email address listed in LAMA, you can use the Notify Applicant button in the Comments form to generate a notification email.
If Notify Applicant is greyed out, that means that the Petitioner doesn't have an email address in LAMA.
The email will include only Open comments, and you can edit the text before sending if you need to.
If the applicant does not have an email address, you must generate a Plan Review Letter (if there's one configured for your module), or use the Generate Document option in the Comments form to create review letter.
The Plan Review Letter can be found on the Documents tab, like any other document.
Generate Document is next to Notify Applicant in the review comments form. It includes the option to select more comment statuses than just Open. You can open it in Word after it's been generated, and it will be saved in the Documents tab like other documents.