Initial file (for example) - JPG, 416kb, grayscale (picture). Result - PDF, 1,08mb. What a problem is in? A result does not depend on tuning DPI (at 72dpi and 300dpi the same result 1,08mb).
It seems to, that this problem appeared since I install other PDF convertor. But I deleted it already, and a problem remained.
P.S. I am sorry for my English. Hope for Your help.