On a Mac, you can print your iMessages from Apple's Messages application. Unfortunately, the Messages desktop app does not display SMS, only iMessages. This results in incomplete conversation threads.
On Windows, there is no equivalent to the Messages app. To view or print text messages on a PC, you will need third party software.
iMazing offers two easy solution to print text messages and iMessages on both Mac and PC:
Anyone who wants to easily print their text messages from their computer.
Download and install iMazing on your Mac or PC computer
To print your messages:
Launch iMazing and connect your device.
In the left sidebar, select Messages. To view your most recent messages, you may need to refresh your data.
If this is your first time connecting your device, iMazing will initiate a backup to pull your messages.
Select the conversation(s) you want to export.
By default, iMazing will export your entire conversation. If you only want to export specific messages, select them now.
In the bottom toolbar, click the Print button. This will open a print dialog box.
In the dialog box, select your print settings and click Print.
Use the CTRL/Command, or SHIFT keys to select multiple contacts or messages.
Selecting multiple conversations aggregates them in the main view.