The following command assigns or remove label to a shared folder

Connect to azure online PowerShell

Connect-AadrmService

Get list of all PDF files only make sure to add the *.PPDF

Get-ChildItem \\servername\foldername\*.PPDF -File -Recurse | Get-AIPFileStatus

Note: Must add justification

Get-ChildItem \\servername\sharename\*.ppdf -File -Recurse | Set-AIPFileLabel -RemoveLabel -JustificationMessage “The previous label no longer applies”

Then to make sure

Get-AIPFileStatus “\\servername\sharename\*.ppdf”

Add any other label to all any extension files

Get-ChildItem drive:\folder\*.docx -File -Recurse | Get-AIPFileStatus | where {$_.IsLabeled -eq $False} | Set-AIPFileLabel -LabelId the ID of the label

for all details

https://docs.microsoft.com/en-us/powershell/module/azureinformationprotection/set-aipfilelabel?view=azureipps