I need to sign a contract PDF and send it back today. I do not have a printer. What is the easiest free way?

You have several free options.

Adobe Acrobat Reader: open the PDF, click Fill & Sign in the right pane, choose Sign yourself, then Add signature. Type, draw or upload an image of your signature, place it on the line and save.

Mac: open the PDF in Preview, choose Markup, then the signature icon. You can sign with the trackpad or hold a signed paper up to the camera.

Windows without Acrobat: in Microsoft Word, insert a picture of your signature into a Word copy of the contract, then export to PDF. This only works if you have the editable file.

A drawn or image signature is fine for many everyday agreements, but some contracts need a certified digital signature. Check with the other side if they require a specific service.

Used Fill & Sign in Reader and sent it in ten minutes. Thanks.