I mostly agree with Lorenzo, with caveats. 

We've got an official policy on this. From that: 

We do not allow spam or commercial messaging not related to EA. We also don’t allow clickbait or other things that interfere with good discourse. However, you may want to advertise an impactful job or opportunity on the EA Forum, which is fine — people have found good applicants on the Forum before, and we’re here to ultimately take action. But you should follow some guidelines: 

• Don’t try to sell it. Try to inform people about the opportunity instead of persuading them to join. It’s nice to mention the weaknesses and downsides of the opportunity, although this doesn’t mean that you should downplay its strengths.
• Make the connection to effective altruism clear, even if it seems obvious to you (unless your organization is a household name in EA). Consider making a case for why this sort of work is particularly impactful (is it neglected?), or why it might be a useful experience for people interested in effective altruism. Alternatively, you can prominently link to other sources that explain these connections. 
  • If you share a job ad that also has interesting content — an explanation of your work and its theory of change, some interesting and relevant news, etc. — more people are likely to see it.

If we end up with a bunch of job listings and/or we start hearing that there are issues due to the job listings, we could change our approach — e.g. by limiting or discouraging listings, limiting where they're shown (more likely), creating separate spaces for them (something I think we should explore), or something else. 

The other thing I'd note is that I think job ~advertisements go better (get more engagement, bring value to people not looking for the job) when they're combined with other content/information, like some explanation of why you're hiring, what your strategy is, an update on what you do, etc. This means that people who aren't interested in the jobs could also get something out of the post, and you might also get more applicants because the post gets more karma (so more people will see it) and because some people who come for the content are also interested in the jobs (this is probably truer for some jobs than for others). 

(I should caveat that I wrote the above quickly (besides the policy excerpt), and without input from others.)