Resizing texture files?

I have tried this countless of times as a .dds file in paint.net, but when I want to import it back to .TgPcDx, RSBin Tools just says: File size doesn'tmatch or something like that. How do I correctly resize texture files?
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https://railworksamerica.com/forum/viewtopic.php?f=29&t=23207
aCup0fBlackTea wrote:I have tried this countless of times as a .dds file in paint.net, but when I want to import it back to .TgPcDx, RSBin Tools just says: File size doesn'tmatch or something like that. How do I correctly resize texture files?