The XPAC fabric of the pack bag is waterproof to 200 PSI. Zippers are not waterproof, but do have a zipper garage. Stitch holes are not waterproof. Zippers are optional on the pack bags, so it is a trade off of convenience vs. water proofing. Stitch holes can be seam sealed to prevent leakage.
So the short answer is fabric will not wet out or leak through, stitch hole / seams and zippers might. Zippers are optional. The day pack is the same material, same limitations.
Blood from the inside washes out very easily and will not stain inside of pack bag. On the outside of pack bag, it is not likely to have a noticeable stain.
