Depends what you mean by PR - if you're a business that makes, let's say industrial rope - then clogging editors' and journalists' inboxes with releases about rope day in, day out won't help you any.
However, if you're creative and you can pitch interesting stats or insights into rope to an industry publication; let's say RopeBlogger - then that's worth a bit more.
With any good PR campaign, you have to look at who you are targeting, what return you're looking for (goodwill? brand recognition? sales?) and how you can measure your investment (with time or money.)
PR is important for the Small businesses to expand their reach and promote their services to the large pool of audience, for example if you are looking to serve customers beyond numerous cities, release a press to promote as you are not doing a common thing, i just post a press release explore it here http://bizpr.co/2016/09/28/get-trending-statistical-techniques-data-collection/