Convert ps to pdf by ps2pdf, but the pdf file is not well-behaved

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http://unix.stackexchange.com – I have a ps file,and converted it to a pdf file using ps2pdf. ps2pdf elden.ps elden.pdf When I open the pdf file in evince, and try to select some text in it using my mouse, the selected content is not the text but some incomprehensible symbols, and also it cost a lot of memory for opening the ps and pdf files and a lot of CPU time for selecting. I was wondering how to convert the ps to a pdf file whose text can be selected and copied, and without much memory and cpu time? Thanks! (HowTos)