PDF to image renders each page at a chosen resolution as a bitmap for previews, thumbnails, or systems without PDF support. Text and vector graphics become fixed pixels and can no longer scale or remain selectable like PDF content.
Clarity and size depend on render dimensions, page count, and image format. PNG suits text and lines, while JPG can suit photographic pages. A scanned PDF is already raster, and a larger output cannot restore detail absent from the scan.