Hi, this error is causing me problems as I can’t merge/flatten pdfs with polyline annotations at present. I’m using 8.7.3 and it’s the same issue as your online sample.
I’ve reported this error before at:
Please advise if this is able to be resolved and/if/or it’s something I’m doing wrong. I need to put the pdf merge into production and polyline annotations are a common use-case for us.