Open a paper in Photoshop.
On a new layer above your paper, use the (1) Elliptical Marquee Tool, and while holding shift (to maintain proportion), click and drag to desired size.
(2) From the Menu Click Edit > Stroke
(3) Stroke the selection 50 px (or desired thickness)
(4) Click on the color box. As you move your cursor over your paper it will turn into a dropper. Use the dropper to click on a color from your paper. (5) Click OK in the color box, then (6) click OK in the stroke box.
Select Color Burn, layer option, in the Layers Panel.
Go to the Layer Styles either from the Menu >Layer > Layer Style > Outer Glow
or double-click to the right of the layer in the Layers Panel - then click on Outer Glow.
Change the color to match the paper just like we did earlier. Then change the Blend Mode for the Outer Glow to Color Burn. Increase the size to desired look.
Do the same thing with Inner Glow.
Very important: Click on Blending Options and decrease the opacity of Fill to desired look. Click OK.
You can add to this by painting more splatters or erasing parts.
If you want other stains on different layers. Just make the shape you want and copy and paste the same layer styles onto the new layer. One way is to right click on the right side of the layer with the effects you want to copy - and select Copy Layer Style. Then move your cursor to the layer you want to make a stain, and right click on the right side of the layer and click Paste Layer Style. However, you will need to adjust the Fill Opacity separately for each layer you copy layer styles too.
You can make text look stained too. Just play with the size of the Inner and Outer Glow Layer Styles to make your stains newer or older (a more crisp edge will look newer - and a softer/bleeding edge will look like it has been around awhile).
NOTE: If you want the stain a color (different than your paper - maybe a jelly stain or something) - just pick the color you want from the picker for the inner and outer glows - and it should be the same color your shape/text is too.