In order to create an embroidery design (such as the .pec file for Brother stitching machines), you have to use a special embroidery software with a digitizing function, i.e. a function that allows users to create vector based designs from bitmap pictures. When using raster files (for example through jpeg to pec conversion), the result typically requires manual tweaking and also experience with embroidery design, because the digitizing function alone is not perfect.
Open JPEG file Open PEC fileAn embroidery designs manager
An embroidery design tool from Janome
An easy embroidery and apparel decoration design software