I have read that google will penalize a website if they do link exchange. Is that true? If I sign up to voltrank will google penalize me?
Links can never get you a penalty as long as they are / to a relevant website. It is the only human input (besides social comments) that SEs can depend upon to see what humans like. Penalty on link exchange is not completely true as most of the Webmasters are utilizing this technique for high SERP rankings... Google will definitely slap a penalty (which can be de-indexing, SERP filter or Ban) on link exchange with junk sites, irrelevant and disreputable links
Buying links can give you a penalty, link exchanging doesn't. However, if you have a page on your site that is a long list of links to completely irrelevant sites and lots of your links come in from similar sources, those link won't carry much weight as they will be deemed irrelevant and unauthoritative. Therefore it may not be massively beneficial
If you are doing link farms and adding irrelevant links on your website, just for PR then Google may penalize your website..
Exchange links with the good website not to bad neighborhood sites. If you exchange links with bad neighborhood sites, you will get penalized from Google
If you are doing link farms and add irrelevant links both techniques are coming in black hat SEO. Google don't want black hat SEO use on your website for getting high pr, so Google penalize your website.
Just do it manually to appear natural. If you signed up with a company then it would just look spamming.