There are some important things to keep in mind regarding the search and use of tests and measures:
Nearly all tests and measures are copyrighted, including those which you can find freely available. As such, you cannot make any changes to the measures, modify questions, etc., without the permission of the copyright holder.
You should ALWAYS contact the author of the measure (even if you find it freely available) to get permission to use the test or measure.
Many publishers/copyright holders place restrictions upon who can use their measures. They do this because they do not want to compromise the integrity of the measures. Further, most publishers will only allow measurements to be administered and interpreted by professionals. You should make every effort to adhere to publisher guidelines for use of the measure.