iMessage/sms

Ok

• Double click on the chat that you want to export
• Scroll to the top, or wherever you want to start from
• Command/P (or click on file and print)
• Select "Save as PDF" from the drop down
• Select where you want to save it to
• Voila...you have a pdf of the whole conversation

The key is scrolling up to where you want to start from.

Hope this helps

Select the thread.

File > Print

Apple does not have a tool for this, but an internet search might find you a 3rd party option.

Do you have access to your Messages account on a Mac?

You can transfer all your messages to PDF or txt files with inexpensive software for your Mac or Windows computer. E.g. search for PhoneView or iExplorer.