just resample it to a larger number in pixels and redefine the dpi as needed or keep it aqs is, or don't even worry about it - some intelligent software like freeware Irfanview to on-the-fly dpi matching when you print. It's all about the pixels you have and supply to the printing process anyway, whether you tell it upfront how many dots to cram into each inch (dpi) or whether it resamples it intyernally makes no difference.

However, you might do this trick: instead of one big resampling from 800 to 3300 pixels (e.g. to match 11 inches at 300 dpi) you might see better results buy resampling not in one fell swoop, but instead in several steps, perhaps going up in increments of 10% to 20% or so, That depends a bit on which algorithm is used when resampling, bell, spline, triangle, lanzcos etc... but in general this can help avoid 'pixelation' or rather a blocky appearance of the few (800) pixels being resized to about 4x their size.The resampling helps in making sure that new pixels are produced in-between by interpolation, but a big jump from 800 to 3300 pixels is a big step and might still leave some artifacts. Doing a few small step resamples to eventually reach 3300 pixels may avoid some of that. Irfanview is a must have for this, so much faster than Photoshop.

I use Irfanview anytime I print something because of the last-minute decisions to print a slightly different size than original image dimensions and dpi might have it.