If you'd like to change your budget during your campaign, feel free! Any increase in your budget goes directly to the search engine provider for your campaign. SiteWit does not take any part of your budget changes.
There can be many reasons for wanting to change your budget. If your keywords are pricey, adding to your budget can help your ads have a better change of displaying and getting clicked. If your campaign's performing well, increasing your budget can drive more traffic to your website.
Feel free to contact support if you have any questions about changing your budget.