Open the PDF in Adobe Acrobat Pro
Go to Print
Select Adobe PDF as the printer
Print the document to create a flattened copy
Save the new PDF
Use a PDF editor with flattening support
Open the PDF
Find the Flatten, Optimize, or Print to PDF option
Apply flattening
Save the file
Use a command-line tool such as Ghostscript
Run a flattening or PDF conversion command
Save the output as a new PDF
Flatten form fields and annotations separately if needed
Remove interactive elements
Save the updated PDF
Check the flattened PDF
Reopen the file
Confirm that forms, layers, and annotations are no longer editable