Spindle Professional generates PDF files with encryption to prevent the file being modified. However, the level of encryption can cause issues with PDF viewers that don't recognise encrypted PDF files, thus prompting the viewer for a password. AES-256 encryption requires Adobe Reader v9.0 and newer to negate the prompt for a password. If you are unable to change your PDF viewer to Adobe v9.0 or newer, Spindle can render the PDF using AES-128 encryption by using an older PDF creation library.

By default Spindle Professional v6 generates PDF documents that comply with v1.7 of the PDF standard with Adobe level 3 Extensions. This standard requires Adobe Reader v9.0 or higher or a compatible viewer to open and view them. Use of this standard allows Spindle Professional v6 to secure documents using AES-256 encryption.

Software Version Tested AES-128 AES-256
Adobe Reader 9.0 and newer OK OK
Foxit Reader OK OK
Nuance PDF Reader 8.1 OK OK
Sumatra PDF 2.5.2 OK OK
PDF Complete 4.1.45 OK NO
Nitro Pro 10 10 OK OK

Versions Applicable

  • Spindle Professional 6

Prior to following the resolution below, please try the resolution specified here: Use Legacy Encryption


1. Open Spindle Professional Tools

2. Expand the Document Automation until you see Email Settings

3. Click on the Advanced tab

4. Select the default attachment type to PDF

5. Drop down the PDF creation library from Default to v3.5.0.101

Documents will have to be processed again for the changes to take in effect.