The present invention relates to a method for improving clarity of a PDF file converted from a paper file. The method comprises: step 1: scanning a paper file to obtain an electronic image file; step 2: determining a top margin, a bottom margin, a left margin, and a right margin of the electronic image file, and deleting data within the top margin, the bottom margin, the left margin, and the right margin of the electronic image file, and converting a first cropped file into a first PDF file; step 3: dividing the first PDF file into some rectangular objects, determining effective areas of the rectangular objects, and deleting data outside effective areas of the rectangular objects, so as to obtain cropped rectangular objects corresponding to the rectangular objects in a one-to-one manner; and step 4: combining the cropped rectangular objects according to same position distribution of the rectangular objects corresponding to the cropped rectangular objects on the first PDF file, so as to obtain and output a second PDF file. By means of the present invention, clarity of a PDF file converted from a paper file can be improved.