Apple script in Automator - to remove same name files with different extensions

The following AppleScript will remove only those JPG with a name matching PDF counterpart. I have tested this with your simple filenames, and examples with your complicated naming examples, and it works identically in Script Editor and as an Automator application using a Run AppleScript action.

Ideally, I would have liked to write this entirely in AppleScript/Objective-C, as the Finder gets lethargic in large file repository processing. The ASOC code would have done the job without Finder to slow it down.

Tested: macOS 11.2.3 on M1 mini.

Code:

use framework "Foundation"
use AppleScript version "2.4" # Yosemite or later
use scripting additions

property NSString : a reference to current application's NSString
property PDF : ".pdf"
# allow for extension case, spelling, and any JPEG2000 files
property JPG_EXT : {"jpg", "JPG", "jpeg", "JPEG", "jp2", "JP2"}


set ff to (choose folder default location (path to desktop)) as text

tell application "Finder"
	set everyJpg to (every item in folder ff whose name extension is in JPG_EXT) as alias list
	
	if everyJpg = {} then return
	
	repeat with thisJpg in everyJpg
		set x to POSIX path of thisJpg
		set thisPdf to (my getBasename(x) & PDF) as POSIX file
		if exists thisPdf then delete thisJpg
	end repeat
end tell
return

on getBasename(afile)
	# return entire POSIX path except extension
	return ((NSString's stringWithString:(POSIX path of afile))'s stringByDeletingPathExtension()) as text
end getBasename

There are two issues:

1. Coding mistake that I have now corrected that stops removing unpaired JPG
2. You are using multiple periods in your filenames that break the code that was meant to only encounter a single (normal) period before the name extension. I will need some time to see if I can work around that issue, as I will have to toss the current handler that gets the basename.
   1. One possibility is to compare JPG and PDF file paths without the extension and if the path strings match and the JPG has a red tag, then delete it.

Try this AppleScript on a test folder containing matching .jpg and .pdf files, before unleashing it on those 6000 files. Note that AppleScript is not the fastest solution for folders with large file quantities to process. The following was tested on macOS 11.2.3.

use scripting additions

property DELIM : {":", "/", "."}

set ff to (choose folder default location (path to desktop)) as text

tell application "Finder"
	set everyJpg to sort ((every item in folder ff whose name extension is "jpg") as alias list) by name
end tell

if everyJpg = {} then return

repeat with thisJpg in everyJpg
	set thisPdf to my getBaseName(thisJpg) & ".pdf"
	if exists (ff & thisPdf) then delete thisJpg
end repeat
return

on getBaseName(afile)
	set {TID, AppleScript's text item delimiters} to {AppleScript's text item delimiters, DELIM}
	set basename to text item -2 of (afile as text)
	set AppleScript's text item delimiters to TID
	return basename as text
end getBaseName

I have something working right now that only removes the extension from the entire jpg file path, which eliminates your having to change filenames. It's working with file1 ... filenn name schemes in Script Editor. Need to create a mixture of PDF and JPG using your longer file naming convention to see how it behaves. Will post when tested in both Script Editor and Automator.

You are welcome. Also, I have a functional Zsh script that does the same thing in far less code, and quicker.