Here is an example of how a careful person with some framing experience, can buy all the framing materials in order to assemble the artwork themselves versus having a professional framer do the work. Included in the shipping tube are print measurements to help the framing process as well as some recommended sizes for mat and frame. The following does not explain how to do the framing. I would not advise learning to frame on any expensive print. The most difficlut part is bevel cutting a mat. Most who frame art themselves, will have a framing service custom cut their mat per below and then simply assembly the frame. There are some links below which explain parts of the framing process and material suppliers.
For the purposes of the example, I will use a well know internet framing service, American Frame. And for a print one of the many 35mm prints which are 12x18 inch size. For those prints, the size of the image plus the digital bevel cut is 12.4x18.4 inches. The size of the mat opening would be 11.75x17.75 inches. The recommended full frame and mat size would be 18x24 inches. And the full size of the print including the white space outside the image area might be 14.5x20.5 inches.
First some comments on the above numbers. The digital bevel cut is 0.2 inches on each side, thus two sides add 0.4 inches. For the purpose of this most common type of framing that can just be considered white space that will not be seen in the frame mounted print. White space around the print is necessary to allow some print sheet area beyond the mat opening for attachment to the mat. On my prints, that is at least one inch outside each image border. The internal mat opening needs to be smaller than the 12x18 inch print size so areas outside the printed image do not show. I have recommended choosing 11.75x17.75 because that leaves a modest 0.25/2 inches = 0.125 or 1/8 inches on each edge of the print under the mat. Too little and it requires more tediously precise positioning, while too much and one loses more of the image. For this size of print, 3 to 4 inch borders tend to look about right. Professional framers may wish to make that larger especially when doing something more fancy as with double mats. Thus the recommended frame size and full mat size of 18x24 leaves (18-11.75)=6.25 inches on the height and like on the width. Note 6.25/2= 3 1/8 which is used below.
At this point the materials selection process is complete. One just needs to Add to Cart and continue on to their checkout area. At the time I am writing this, the materials cost would normally be about $31 but because they were having a special on the mat, the cost was less than $24. And shipping would add at least $6 more. If one had instead chosen a better quality Bainbridge Alphamat Artcare 8517 black for the mat, the cost would be about $4 more. For large frames, there is an additional cost of $25 if the oversized package shipping limit is reached. Note to mat my largest size 6x7 prints, which is a 23.6x29.6, requires a 32x38 inch mat that can be cut from stocked 32x40 inch sheets. For large format prints as 30x38 inch size, requires at least a 38x46 inch mat. That requires cutting the mat from a large 40x60 sheet which is usually only stocked by high end professional framers. Note from American Frame one can purchase larger frames but not larger than 32x40 mats, glazing, or backing boards. Thus for large format prints, one ought to have a local framer do the work because shipping costs are too high for such internet framing services. Alternatively if one lives near a large urban area, an art supply shop may carry the large sheets. If so they likely also can bevel cut the mat.
The following site has an good description of do it yourself archival matting as well as links to material suppliers at the bottom of the page:
http://www.nedcc.org/plam3/tleaf66.htm
The following site describes a range of Crescent mat papers:
http://www.britecores.com/pig0506.html
Yahoo listings for Art and Framing.