1. Please press Win+R, type "regedit" and click OK. 2. Please search for the following node: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\FipsAlgorithmPolicy
3. Doubleclick on the key "Enabled" (as shown in step 2 on the screenshot). 4. If this key has the value 1 please change it to 0 (as shown in step 3 on the screenshot). 5. Close the Registry Editor. 6. Try to add the PDF folder again.