How do I lock a PDF document with a password ?

Follow these steps to secure your PDF document with an Owner Password and a User Password

1. Define the permission that will be granted to user

   import (
     "github.com/unidoc/unipdf/v3/common/license"
     "github.com/unidoc/unipdf/v3/core/security"
     pdf "github.com/unidoc/unipdf/v3/model"
   )
   
   ...
   
   permissions := security.PermPrinting | // Allow printing with low quality
     security.PermFullPrintQuality |
     security.PermModify | // Allow modifications.
     security.PermAnnotate | // Allow annotations.
     security.PermFillForms |
     security.PermRotateInsert | // Allow modifying page order, rotating pages etc.
     security.PermExtractGraphics | // Allow extracting graphics.
     security.PermDisabilityExtract // Allow extracting graphics (accessibility)
   
   encryptOptions := &pdf.EncryptOptions{
     Permissions: permissions,
   }
   	

2. Supply the Owner Password, User Password, and permissions above into Encrypt function

   pdfWriter := pdf.NewPdfWriter()
   <br>err := pdfWriter.Encrypt([]byte(userPassword), []byte(ownerPassword), encryptOptions)
   	

3. After you can use the pdfWriter variable to write a the pdf document

For a complete example on how to lock your PDF document, see this code example

https://github.com/unidoc/unipdf-examples/blob/master/security/pdf_protect.go