300 DPI is the ideal print resolution for digital printing machines. The design of a file with a resolution of less than 300 DPI will result in blurring and pixelation. On the other hand it is not worth designing with a resolution higher than 300 DPI. To the extent that it is possible to judge by the eyes there will be no difference in press quality. In addition it will make your file much larger (it will increase the upload/download time).
We always recommend drawing with 300 DPI for printing but we also know that sometimes you can t edit the projects. If you cannot design your files to print at 300 DPI you have to take some steps to ensure that the low resolution works for you.