How to clean up a jpeg scan of document which has many black pixels. Here is a document. I am new to using affinity photo. Have been using photoshop

[chet]

[Michail]

@chet, welcome to the forums here 

You can try the "Blemish Removal Tool" or "Inpainting Brush Tool". Check the help to see how these work and get started.

[loukash]

Since this is technically a 1-bit scan, it can be tough to clean up.
I would scan again as RGB – or ask the source for a new scan in RGB.

Else you may want to experiment with live effects: blurs, dust&scratch etc. to remove all those "dithered gray" standalone pixels globally.
As a side note: always work at 100% zoom on similar pseudo-1bit images!

On a quick try, Diffuse Glow seems to work pretty well:

[lacerto]

Obsolete.