[jl6]

I guess you could, but this is the source of the errors (actually warnings) that the article mentions. Probably best to fix the file with the provided tool (fix-qdf is distributed with qpdf) rather than get in the habit of ignoring warnings.

[gpvos]

OK. I have never needed or used fix-qdf and forgot about it, so your typo (fix-pdf) made me think it was from a different package.