SetDirectory["C:\\drorbn\\AcademicPensieve\\Projects\\Theta\\LinkFigs"]

fs=FileNames["*.ps"];

Do[
WriteString[StringReplace[f,"link"->"L"],
StringReplace[ReadString[f], (x:NumberString)~~" setlinewidth":>ToString[3ToExpression[x]]<>" setlinewidth"]
],
{f,fs}
]