Swedish tracing paper makes preserving your precious patterns possible. Say that three times fast! I think it is safe to assume that we ALL have been through the disappointing scenario of cutting out a pattern size that we think will fit, sewing it to completion and finding that, ugh, we should have cut a size up or a size down!
You can change part of that outcome if you first trace your supposed size, along with all markings, onto swedish tracing paper and use that as your pattern instead. Like magic, your pattern will remain as intact as the day you bought it. Yes it is another step, but it gives you future size options and the ability to share your pattern with others or make your friend of a different size a version too! (hopefully out of different fabric) :)
This fanciful misnomer of a product(being neither Swedish nor paper) is sold as a 29"x10yd roll. It is a durable yet soft and pliable (similar to a non-woven interfacing) material that marks easily with most any tool. I typically use a felt tip marker with a light hand so that it doesn't bleed through. Pencils, chalk and non-inky pens work great as well. Swedish tracing paper has some tooth which allows it to hold to fabric requiring few weights or pins while tracing. Unlike freezer paper (which some use in a similar way), this tracing material uncurls or relaxes from its tightly rolled packaging with little help.
Some folks will even baste the tracing paper pattern pieces into a mock-up garment in order to address fitting issues. Like I said, it is durable stuff and can actually be ironed as well! All of us Bolt gals use and love swedish tracing paper and hope you will give it a try if you haven't already!