It may sound trivial, but maybe it's not.
If I'm looking for a job then I look to a company's website open positions page and I send a CV (curriculum vitae). In this case the company would be my employer.
If instead I'm a freelancer and I'm looking to get a job then I try to contact the company to advertize my services. In this case the company would be my client.
Is there something in between? Think of a company that needs a service (the development of a web application or something similar) for which it may hire somebody or may outsource it to a freelancer. In this last case the distinction between employer and client, according to me, is not so clear.
So the question is: do you think it makes sense to submit a CV to a company's spontaneous applications page (where they seek an employee), and to write in the covering letter that I would be glad to work for them as a freelancer in the case they need one for a service involving the skills I have?