Assign sequential numbers to title metadata

[wlg.graham]

So I have a folder of probably 2,000 pdf files. I need to add a sequential numbers starting from 1 to the start of each PDF metadata title for all of the files in the folder. Is there a good way to do this efficiently?

[StarGeek]

Try
exiftool "-Title<${FileSequence;$_+=1} $Title" /path/to/files/

This command creates backup files.  Add -Overwrite_Original to suppress the creation of backup files.  Add -r to recurse into subdirectories.  If this command is run under Unix/Mac, reverse any double/single quotes to avoid bash interpretation.