This question already has an answer here:
I am using online job portals to search for suitable opportunities. I think that, since the website is visited by several employers, there is no point in uploading a cover letter to the website's database as the cover letter must be customized for individual organization.
However, when I apply for a particular position in a company, I attach my resume and cover letter as two separate PDF documents. Is it better to combine them into a single PDF file with the first page being the cover letter followed by the resume? Or should I send them as two separate documents?