I made a nuget package that uses Pdfium to do exactly what you want, well except it returns a bitmap list, but trivial to use Save() to save as jpegs. I use this in production software to convert Pdfs into images for viewing within a WinUI3 application. 100-page document at 300 dpi would probably take around 7 or 8 seconds or so. I am not sure what is an acceptable speed for you.

Nuget package is PdfToBitmapList.

Can pass file path of pdf, memorystream, or byte array.

Use like: var imageList = Pdf2Bmp.Split(pdfFilePath)

There is an option to save images to disk by passing in a save location like :

var imageList = Pdf2Bmp.Split(pdfFilePath, "C:\TempDirectory")

This is very useful for larger Pdfs as holding all those images in memory can eat up your ram very fast. Instead of returning a List of Bitmap images it will return a list of strings with the paths the images are saved on disk. This requires manual clean up after the conversion, so just keep that in mind or save location will have tons of leftover images.