In the presented work, the developed by author segmentation technique based on P system is applied to pre-OCR enhancing of document images. Developed for solving the noisy medical imaging problems, the proposed technique has the advantage features, which ensure successful application to the historical document images enhancement problem. The first advanced feature is the high sensitivity of the P system based algorithm, which recognizes the tiny details. Another advantage of the P system based algorithm is its natural parallelism that allows parallel processing of regions of a huge image. The use case of the proposed work is old books printed in Romanian Cyrillics. Keywords: document image enhancing