How to print and/or export a Messages app conversation containing many individual text messages?

I recently needed to export to a PDF file an Apple Messages app conversation stored on my iPhone.

Googling offered solutions, but none preserved the Messages App's formatting and time stamps.

After much experimenting, here is what I did which worked for me:

Problem: How to “print” or “save to file” a Messages app conversation containing many individual text messages while preserving Messages app formatting and time stamps.

Devices:

• iOS 15.6 operating system on iPhone 13 Mini using Messages app to send Messages App texts and receive SMS text messages. 
• Google Android phone sending SMS text messages to and receiving messages from my iPhone 13 Mini.
• MACOS machine running “High Sierra” version of MACOS (10.13.6) and Messages app, Version 11.0 (5500).

The following procedure may not work as described if the MACOS, iOS, and Messages app versions you are using differ from those defined above.

Procedure: 

1. Synchronize your iPhone Messages app with iCloud:
   1. On your iPhone, go to: Settings > Your Name > iCloud .
   2. Locate the Messages app in the list of apps on your iPhone which can be synchronized with iCloud.
   3. If the Messages app is not already turned on for iCloud synchronization, then flip the switch to turn it on. The switch should change color from gray to green. This action should start the uploading of your text message conversations to iCloud,
2. Synchronize the Messages app on your MACOS machine with iCloud:
   1. On your MACOS machine, go to: Apple icon > System Preferences > iCloud.
   2. Make sure you are signed into iCloud. If you are "signed out" or have never setup iCloud, do so now.
   3. Open the Messages app on your MACOS machine.
   4. In the Messages app, go to: Preferences > Accounts and select the account you are using for your messages.
   5. Make sure the checkbox labeled "Enable Messages in iCloud" for this account is checked.
   6. Depress the "Sync Now" button to upload and synchronize the text messages on your iPhone with iCloud and synchronize these messages with the Messages app on any of your other iCloud enabled Apple devices (MacBook, MacMini, iPad, etc.}.
   7. Close the Accounts dialog screen.
3. Wait for your text message conversations to synchronize across all of your iCloud enabled devices. Depending on the number of messages you have on your iPhone and MACOS computer, it may take a significant amount of time for your messages to sync with iCloud, your iPhone, and your other iCloud enabled Apple devices.
4. Wait for the Messages app conversation of interest to appear in your MACOS machine's Messages app.
5. Make sure the conversation of interest is fully synchronized between your iPhone and MACOS machine (i.e. look at the text messages within the conversation on both machines to make sure they are the same).
6. In the Messages app on your MACOS machine, select the conversation to be printed and/or exported.
7. Scroll to the oldest text message within this conversation where you want to start printing and/or exporting. Click on this message to highlight it.
8. Select File > Print in the Messages app menu. Note: depending on the number of messages selected and the speed of your MACOS machine, it may take some time to display the print dialog screen.  
9. When the print dialog screen displays, check the "print preview" contents to make sure the selected messages within the selected conversation are the ones you want.
10. Select “Print” or “PDF > Save as PDF” to print or save the selected portion of the Messages app conversation to a file and folder of your choice.

Notes:

• The Messages app conversation I processed contained hundreds of text messages sent over a period of 6 weeks. 
• When printed, my iMessage conversation was 118 pages in length.
• This procedure preserved the Messages app's text message formatting and time stamps,
• After downloading the messages conversation PDF file, I used PDF Expert to annotate and edit this conversation for my own purposes.