If you want to remove FileOpen DRM protection from a PDF, follow these steps. Note that this method will only work on a system that already has the necessary permissions to open the DRM-protected PDF.

Manual Method-

Download De_DRM_tools from here

Unzip De_DRM_tools-master.zip

Within the new folder DeDRM_tools-master, navigate to \Other_Tools\Tetrachroma_FileOpen_ineptpdf

Right click and open the file ineptpdf_8.4.51.pyw 

Additional files to install are-

1)Python 2.7 download here

2)PyCrypto

3)PyWin extension

4)FileOpen plugin

• Open Command Line in the folder C:\Python27\Scripts -> This can be done by navigating to C:\Python27, hold shift, right click on Scripts and press 'Open command window here'

•To install PyCrypto, type pip install pycryptodome

• To install the PyWin extension, type pip install pywin32

• To install the FileOpen plugin, go to https://plugin.fileopen.com/ and install the latest version

• Navigate back to the folder C:\Users\XX\Downloads\DeDRM_tools-master\Other_Tools\Tetrachroma_FileOpen_ineptpdf

• Right click on ineptpdf_8.4.51.pyw

• Navigate to line 2285 and change the value of x in 'self.fileopen['Build']='x' to the build number as shown on the FileOpen plugin page (Windows Installer link)

• Double click on ineptpdf_8.4.51.pyw

• Ignore the Password or Key file box, press the dots to add an input file, type the name of the decrypted output file and press decrypt.

• Decrypted file will appear at C:\Users\XX\Downloads\DeDRM_tools-master\Other_Tools\Tetrachroma_FileOpen_ineptpdf