Originally Posted by Ulodesk

Jamal,
Jpeg, of course, turns the PDF into an pixelated image. The resolution set for the conversion will detrmine the extent to which the quality erodes at various magnifications. This may depend on the options provided by your PDF software. In a recnet Acrobat Pro version, there are various quality settings for the conversion to jpg, including up to 2400 ppi resolution.

Originally Posted by Ulodesk

Best must defined by your usage and the original material. Curves and slanted lines naturally cause the major problems in conversion to square blocks (pixels), along with tonal and color gradations. However, there is a trade-off between file size and resolution. The finer (higher) the resolution, the larger the file size.

Beyond that, there are undoubtedly issues which a graphics or PDF expect would know that I don't, as far as settings are concerned, and you might try searching under those terms in fora other than this one.