Search the Knowledge Base for article 19556 or 'Unable to process the Lockfile'. This always works for us.

The knowledge base is down. Does anyone have the article or the solution?

If issue is happening in Windows 10 or Windows 8, then the shortcut to Sage 100 may need to be set to "Run as administrator" or the Windows Registry key for Sage 100 PDF Converter may need permissions modified.
However, the Knowledgebase Article 19556 is a popular one for the "Unable to process lockfile" error, here is the contents of that article:
Error: "Unable to process the Lockfile: Crystal Reports ActiveX Designer - <report or form name>. Processing cancelled" when printing to Paperless Office PDF
Products : Sage 100

Disclaimer
Operating System Warning
This solution requires advanced knowledge of your computer's operating system. Contact your system administrator for assistance. Modifying your Windows Registry incorrectly can severely affect system operations. Sage is not responsible for operation issues caused by incorrectly modifying your Windows Registry. Always create a backup of your data before proceeding with advanced solutions.

Resolution

Delete any Jobs and Locks folders under the Sage PDF Converter key in the Windows registry.

Note: For Sage 100 ERP version 2013, Product Update 8, version 2014, Product Update 4 or higher, and later versions, the name has changed to Sage 100 PDF Converter

Note: It is only necessary to delete the Jobs and Locks keys in "HKEY_CURRENT_CONFIG\Software\Sage PDF Converter":

From the Windows Desktop, click Start, Run
Note: For Windows 7, click Start, and use the Search Programs and Folders field
Enter regedit
Click OK (if available) or press the Enter key
Expand HKEY_CURRENT_CONFIG key
Expand Software Key
Expand Sage PDF Converter key
Locate the following folders (if they exist):
Jobs
Locks
Expand the Jobs key, and delete any subfolders
Note: Subfolders may prevent the Jobs folder from being deleted.
Expand the Locks key, and delete any subfolders
Note: Subfolders may prevent the Locks folder from being deleted.
Delete the Jobs and Locks keys
NOTE: If the Registry key cannot be located here, reinstall the Sage PDF Converter using Paperless Office Advanced Options. If the Registry key is still not present after reinstalling the Converter, contact Sage Customer Support to provide a copy of it for you, or export it from a working workstation under the same location (HKCC/Software) then import it onto the affected machine.

For Terminal Server and Multi-User Systems:

Go to Devices and Printers in Windows
Remove any "Redirected" Sage PDF Converters. These will normally say something to the effect of Sage PDF Converter (Redirected) or Sage PDF Converter (From Session 9)
Ensure there is only one Sage PDF Converter located in Printers and Faxes, and make sure it is not redirected.
On the Windows Start menu, click Run.
In the Open field, enter Regedit and click OK.
Expand HOTKEY CURRENT CONFIG key using the Plus symbol
Expand Software Key
Ensure that the Sage PDF Converter key is present and has 39 values associated with it. If there are no values or if there is only one value that shows "REG_SZ", Uninstall then Reinstall the Sage PDF Converter on the Terminal Server.
If the Registry key is still not present after reinstalling the Converter, contact Sage Customer Support to provide a copy of it for you, or export it from a working workstation under the same location (HKCC/Software) then import it onto the Terminal Server
If the issue persists after processing these steps, there is a possibility that the system does not like the target directory specified in the Paperless Office Maintenance Task. Verify that the Storage Location for the PDF Document(s) being printed is a location on the Sage 100 Application Server. If the issue persists, try pointing the PDF Directory to a folder within the MAS90 folder. Network permissions (especially with Sage 100 Advanced) can play a role in causing this issue.

ID:19556Last Modified Date:4-9-20161460220684833

If you are using an older version of Sage 100 which uses the "Sage PDF Converter" (not the Sage 100 PDF Converter) then this might be helpful too:

Make sure there is no stuck print job in the Sage PDF Converter printer
Access Start, Control Panel, Devices and Printers
Right-click Sage PDF Converter
Select See what's printing
Go to Printer, Cancel All Documents
Verify Sage PDF Converter printer settings in Devices and Printers
Access Start, Control Panel, Devices and Printers
Right-click Sage PDF Converter
Select Printer Properties
On the Ports tab, make sure the default port is a Local Port "Sage"
On the Security tab, set Everyone to have rights to the following (select the check boxes):
Print
Manage this Printer
Manage Documents
Click OK
Access the Windows Registry of the workstation and delete Jobs and Locks folders belonging to Sage PDF Converter

Warning: Familiarity with navigating and editing the Windows Registry is required. Make a backup of the Registry before attempting to edit.
Open Registry Editor:
From the Windows Desktop, Start button / Run (or Search Programs and Features) / REGEDIT
Under "HKEY_CURRENT_CONFIG\Software\Sage PDF Converter" if either of the following folders (keys) exist, right-click each such folder (key), then select Delete:
Jobs
Locks
Go to File, Exit to close out of the Registry Editor

I set my Sage 100 to "Run as Administrator". It worked! Thank you for such a simple fix. Try this before everything else.