PDFs are fine too. I'd rather say less in the email to get them focused on the cover letter that I've so carefully crafted. Links in the email will again distract them from reading the letter and may take them to a place where they will discover something to disqualify you. Why send them to Linked in when they can read your letter and see your resume immediately? If you have information at Linkedin that is better than what is in your letter or resume, then why isn't in you letter or resume? Keep the reader focused.