[I have already posted this on the pdftex list, but nobody has answered.]
I have a file with many figures made by pspicture. Unfortunately,  this hinders the using of pdftex and microtype. 
Adding \usepackage{pst-pdf} after \usepackage{pst-plot,multido,pst-tree} does not work. Has anybody a better idea ? 
André Bellaïche