is lime juice as acidic as lemon juice and therefor uses 1:1 substitution with lemon juice to ensure low acid food is acidic enough for boiling water canning?
Yes, for the most part, limes and lemons can be used interchangeably in recipes. However, it's important to note that lime juice is more acidic than lemon juice, so you may need to use a little less of it than what your recipe calls for. The general rule is 3/4 cup of lime juice substitutes for 1 cup of lemon juice.
In the US, most canning recipes produced by authoritative sources use bottled lemon juice not fresh. Bottled lemon and lime juices are produced with a standardized acid level. pH in fresh lemons and limes can vary considerably , depending on freshness, storage method, variety and growing conditions.
That being said, the pH of fresh limes on average is slightly lower than fresh lemons, so you could substitute fresh lime juice for fresh lemon juice 1:1 without a problem.
Bottled lime and lemon juices can be used interchangeably 1:1.