If a user is purchasing
something on your website it is absolutely necessary to reassure the visitor
that their purchase and online security is safe on your site. The security
seals not only need to be visible on your page but they should be shown in
close proximity to any checkout or order form buttons to alleviate any anxiety
about the threat of online security.
The industry standard says yes, with a caveat. Adding trust and security seals has time and time again proven to increase conversions by easing customer's fears when interacting with new businesses.
The caveat is that, regardless of industry standards, this will need to be tested for your products as well. I've read about companies that tested removing the trust seals from their sites and unexpectedly saw conversion lifts upwards of 25%. It's results like these that really drives home the fact that A/B testing is more important now than ever.
In regards to your question, I would suggest adding web security and trust seals to your pages with the understanding that removing those security seals may be an A/B testing option you may want to look into in the future.
The popular drag and drop page builder Unbounce reported a Wider Funnel study that showed using the McCafee seal decreased the conversion rate by 1.65%, although they note that this could be because of the particular placement of the seal.