"Pay rate DOE" means that the wage for a position depends on experience. Companies will typically include this disclaimer in a position announcement without a salary; however, sometimes they post a range.
When a company posts a position without a salary, it has more leverage in salary negotiations. Posting a position with a salary range allows a company to weed out those who would not find the highest wage acceptable. The range of wages increases as the level of the position increases. For example, executives receive salaries in a wide range and entry level employees receive wages in a much narrower range.