How to Lock a PDF from opening
You can use either passwords or certificates to lock a PDF file from opening but they both have their problems.
A more secure and easier way to lock a PDF from opening by unauthorized users is to use encryption with licensing controls and transparent key management. You therefore do not have to worry about key distribution. This is what Locklizard uses along with device locking to prevent encryption keys (and theforefore your documents) from being shared.
How to Lock a PDF from editing
Most PDF editors enable you to lock a PDF from editing. However these restrictions can be easily removed – see locking PDFs with Adobe Acrobat below.
Locklizard automatically locks a PDF from editing when you protect it. Users cannot edit content or copy/paste it to other applications. You can also lock PDF forms so that form fields cannot be edited and modified in any way but the user can still enter text in the fields provided.
Locking PDFs with Adobe Acrobat
Adobe Acrobat lets you lock PDF files (encrypt PDFs) with a password so that they are set to view or read only (lock a PDF so it canot be edited). You can lock PDFs so they cannot be copied, printed or edited.
However, the only protection available is the password which can be easily removed using freely available PDF password removal tools. Once the password is removed the recipient can do what they like with the file.
How to lock PDF from editing with a password:
- Open a file in Acrobat PDF Editor and select Tools > Protect.
- Select the option to restrict editing with a password.
- Make sure Changes Allowed is set to ‘None’.
- Enter a password.
- Click OK and then Save.
You can also apply a document open password but that does not prevent users removing the restrictions. Anyone that has the document open password (hint: any user you share the PDF file with needs it) can remove the PDF restrictions in seconds.
So the Adobe method of locking PDFs to prevent changes provides zero protection since it can be easily defeated.
Locking PDF files online
There are many PDF tools similar to Adobe that let you lock a PDF online. The problem however is that you have to upload your unprotected PDF files to a cloud server where they could be compromised. This might be OK for non sensitive or confidential PDF documents but most businesses do not want to expose their documents to a third party which is why they are protecting them to begin with.
So while online PDF locking tools may seem attractive, they are actually less secure and provide only simple password protection which is easily removed.
Locking a PDF with Safeguard PDF Security
Safeguard PDF Security locks PDFs (encrypt PDFs) using public key technology. There are no passwords to enter or remove or certificates to manage.
When you protect a PDF file, a corresponding key for the document is relayed to a server and stored encrypted. This key is transferred in encrypted form to an authorized user’s computer when they open the PDF document. The key is held encrypted in a keystore and the keystore is locked to the authorized computer so it cannot be moved to another device.
How to lock a PDF file from editing without passwords:
- Right-click on a PDF file in Windows File Explorer
- Select the option ‘Make secure PDF’
- Press the Publish button
The protected PDF file is now locked from editing, copying, printing and screen grabbing – all of these security controls are enabled by default. You can optionally add watermarks that cannot be removed, add expiry to the PDF, and lock PDF orientation so it cannot be changed.
Safeguard PDF Security locks PDF files (encrypt, apply DRM and licensing controls) so they cannot be be copied, printed, edited, saved as (saved in unprotected form), or screen grabbed, and enables you to add dynamic watermarks to printed and viewed documents.
When you lock a PDF file using Safeguard PDF Security it encrypts the document and applies DRM controls – document protection is enforced no matter where the PDF file is stored or who it is sent to. PDF files are are locked to machines (devices) so they cannot be shared. If a locked PDF is sent to a unauthorized user they will not be able to open it since they need a decryption key. If a user forwards on their license file to another user then it will not activate since it is a one time use.
How to lock a PDF form after filling out / fillable fields in PDF files
You can use Safeguard PDF Security to lock PDF forms and form fields from editing and from form submissions from being altered after they have been filled out.
If you have a document that contains a form then it will automatically be protected from editing – users can fill in fields but cannot edit form content. You can also encrypt form fields on submission so that data in PDF form fields cannot be changed.
For more information see locking fields in PDF forms.