Wikimedia UK notes with interest the article published by Times Higher Education today entitled: “PR staff strive for Wikipedia whitewashes”
Wikipedia guidelines state that editing articles about yourself, your institution or, in the case of PR, clients that you represent, is a clear conflict of interest and should be avoided.
As this report shows, attempts to remove negative, reliably sourced information from a Wikipedia article tend not only to be reverted but attract more attention to that material.
In terms of correcting factually inaccurate content the best course of action is to propose changes on the talk page of the article and be honest about who you represent. You can also note your question on your user talk page, ending with the tag {{help}} which will notify some experienced Wikipedians that you need some assistance. You can also email info@wikimedia.org.uk for some advice.