This paper proposes a print-and-scan (PS) resilient watermarking scheme based on the mean of DCT coefficients (MDC) for a fixed AC frequency of image. We investigate the property of MDC in the PS process and find that the MDC is nearly unchanged after PS, which is approximately zero for natural (non-watermarked) images. The watermark bits are embedded by shifting these PS-invariants to be positive or negative. The embedding intensity of the scheme is determined by a JND model to avoid the visible distortion. Experimental results show that the scheme can successfully resist the PS attack in different printing status.