I don't think there is an official guide, I think the only thing official is setting up custom sensors in PRTG to grab stuff from Lansweeper.
I do a lot of things that aren't supported, so I'm hesitant in telling you how... BUT... here's what I do:
PRTG to Update Lansweeper Classic: CURL call to PRTG API, download JSON results to file, SQL stored procedure to import JSON file and update LS records accordingly.
Lansweeper Classic to update PRTG: Powershell, PRTG module, sqlserver module... query custom report via SQL View SELECT, pass appropriate fields to PRTG via powershell module commands.