How to save iPhone text messages to PDF: Download the free trial of Decipher TextMessage and install the software on your Windows or Mac computer. Open Decipher TextMessage, select an iPhone, and choose a contact whose text messages you want to save as PDF. Step 1: Launch the Program and Connect iPhone to the Computer. Launch the program and connect your iPhone to your computer using a USB cable. Now, you will be able to see your iPhone text messages on the programs's user interface.