There is not a figure for acceptable validity of a psychometric test. When scrutinizing test manuals, the qualified user is recommended to assess whether or not validity studies have been conducted and whether they are criterion or construct validity studies. If you will be using your test in a norm referenced manner, construct validity is essential. If you will be using your test in a criterion referenced manner, criterion-related validity is more important. You also need to check who the study was conducted on, how many respondents were involved, whether the criteria used was both reliable and valid# and whether any noted correlations* were statistically significant given the stated sample size.
* E.g., a correlation between similar scales on 2 different tests for a construct validity study or correlation between test score and performance in a criterion-related validity study.
# The criterion (e.g., performance appraisal scores) must be consistently and accurately assessed and must really measure what it claims to measure, i.e. performance, time management, customer service skills etc.