According to Wikipedia, foxing is an age-related process that causes spots and browning on old paper. It does not affect the actual integrity of the paper. Tanning is a similar process where paper has gotten yellowish-to-brownish with age.

Yes. Pattern Grading is commonly used by home sewists and seamstresses to get a good fit. Here is a helpful article from Threads Magazine:

http://www.threadsmagazine.com/item/4368/making-sense-of-pattern-grading

Back in the early days of commercial sewing patterns, the technology of adding ink onto tissue paper had not yet been developed. Those early patterns without ink are commonly called Unprinted Sewing Patterns.

Unprinted patterns were always sold one size per package. A factory folded unprinted pattern will have all the pieces individually cut out and folded neatly together. Unprinted pattern pieces often have tiny dots punched out in the shape of letters (A, B, C, etc) or numbers (1, 2, 3, etc) so the home sewer can easily identify the unmarked pieces.

Pattern size numbers have changed many times over the last 100 years. It is recommended, when possible, to choose a pattern whose measurements (bust, waist, hip) are as close to your own as possible.

VERY EASY: easiest, quickest patterns to sew. Great for beginners. Perfect for easy-to-sew fabrics.

EASY: more sewing details than Very Easy patterns. Great for those with limited sewing knowledge and some fitting knowledge.

AVERAGE: require experienced sewing skills and take more time to complete. Expect more fitting & inner construction. Find more variety in fabrics from stretchy knits to synthetic leathers & suedes.

ADVANCED: for those who like the sewing challenge of professional tailoring and fine couture techniques. Expect intricate fashion shaping, hidden construction details, couture inner construction, fine touches of hand sewing and bias draping.