Ideas for effective cold emails/LinkedIn messages to recruiters?

I just registered for LinkedIn Premium and am hoping to connect with some recruiters via Inmail. Has anyone had any luck with this feature?

Can anyone recommend some strategies for effectively reaching out to recruiters in the marketing/PR/communications sector?

Are cold emails and Inmails acceptable or distracting? Should I include a link to my account or try to add a PDF of my resume?

How specific should the email be about why I'm contacting said recruiter?

Thanks for any insight you can provide.

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