• Open or create your PDF document in Nuance PDF as normal. Click on the lock symbol found on the left hand tool bar.
• Click on the '+' symbol on the top left hand corner (above Password Security)  
• You will see a new Security Scheme window opening, Type a Scheme Name (Whilst it can be anything, you can use the scheme you are creatoing to secure any future document with a single click so naming it something sensible would be useful) and Click next.

                            

• Please tick the boxes 'Use Password' and 'Save Password with Scheme'. Click 'Next'.

                           

• Under 'Document Restriction' use the drop down box of 'Compatibility' - select 'PDF 1.7 and later (256-bit AES - High Security)'. Then tick the box 'Allow Document opening only by Password'. In the box below it, please enter the password you wish to secure the PDF with.

                                       

• Once done, click 'Next', where you will be prompted to enter your chosen password again. Click 'OK' and press Finish at the end.

                   

• You will now see the name of your security scheme on the left hand side next to the lock symbol, under Password Security Heading. In order to apply this scheme to your open document, right mouse click on your scheme name and select 'Apply Security Scheme'. The Security Scheme will then apply the next time you save the document. It is worth noting that the scheme you have created can be applied to future documents by simply visiting the symbol, right mouse clicking your created scheme and applying it.

Important: keep your passwords in a safe place. If you lose or forget the passwords used to encrypt modern documents, they cannot be recovered.