Thanks for these answers.
In the 21st century, we can use various electronic forms and read books in this way. But I dont think that the use of paper for something useful, for example make rich our knowledge is a waste of paper. Most of the older generation I know chooses the traditional way of reading.
Polaris Viewer 4.1 on Galaxy S2 is pretty good in trying to rebuild text from pdf-files to screen size.
But I offen transform pdf to plain text by means of pdftotext-utility for Linux, assuming that tables, equations will be garbled and images will be thrown. Further I can wrap the text into epub-file through sigil, and if I would be not so lazy, I will put the images from pdf to respective pages in epub.