Affect of changing content on rankings

We are currently changing content on some of our web pages. Obviously we are hoping it's an upgrade and helps us rank higher and also make sure we don't get any sort of duplicate content type penalties. We have a lot of locations pages and we had about four articles written that we just circulated throughout the locations pages with minor changes to some, if any of the articles. There are other parts that somewhat describe the location but there has been no notification on anything that we have duplicate content so I don't know if it even matters.

Anyway, time for the question. Some of these areas we already rank fairly high for e.g. 1-4. Could changing the content have a negative impact in the short term or is this definitely something we should be implementing throughout the site? It's tough to come up with solid, unique content on essentially the same subject other than location for locations pages but it's absolutely necessary and obviously a lot easier when we just pay for it but costly.

Changing content can have a negative impact. Be careful that you don't reduce the relevance to the keyword. Focus on improving the content offered by your competitors.