I don't think anybody would say adding arbitrary steps is a best practice! But what does that (possibly) extraneous click do? Is it a checkbox that is proven to (or reasonably thought to) help with lead scoring?
Keep it as little as possible.
Yet, I prefer that after filling out the form people receive an email with the download link (and you make it clear on the LP). Meaning you will have one more click. The reason for this is that it forces the lead to provide you with a valid email address. The rationale is that you are in the lead generation business, and a lead without an email address is close to useless and impairs the ROI of your campaigns.
I observe that this is a discussion that we often have with web specialists or communication services. For them, any additional click is a sin. But they do not get paid on number of opportunities, they usually get paid on what some call vanity metrics (number of visitors, SEO rankings, ...).
I agree that you should minimize the "friction" in the process and agree with Greg that the email forces the lead to provide a valid email if they really want the asset.
What you want to avoid is a process where you have 3 clicks to get to the form itself or 3 clicks to get the paper after they click the email link.
In this case it sounds like 2 clicks to get the download after clicking the email. Which IMO could be other good or bad depending on what value is gleaned from that widget. If you have two buttons for someone to "self-score" her/himself before they click to download, that might not be bad, depending on how it's phrased and what value it's proven to have.