Maida is wheat flour similar to what is sold in the US as cake flour. Like cake flour, maida is finely milled, and it has less protein than all purpose flour. You can use it for bread and cakes, as well as chapatis, parathas and puris.
To achieve a flour more like all purpose or other flour types, you can add gluten to maita. According to The Fresh Loaf, maida typically contains 7.5% gluten (if anyone can find a more authoritative source, please edit accordingly).
Cooking for Geeks has a good article about the gluten content of other flours:
High gluten flour and bread flour is produced from hard wheat. High gluten flour has a gluten percentage of about 12-14% while bread flour contains about 10-13% gluten. Both flours are almost completely made of hard wheat, but some high gluten flours are treated to reduce starch content, raising the gluten content to around 14%. These flours are generally used for making breads. High gluten flour is reserved for breads that are extra elastic such as bagels and pizza.
Cake flour is produced from soft wheat and is low in gluten content (8-10%). This flour is used for making delicate cakes. Baked goods made with cake flour has a tendency to crumble because of the low gluten content.
All purpose flour is made from a mixture of hard and soft wheats. The gluten content ranges from 9-12%. This is the most versatile flour because it can be used to make both cakes and breads. However, breads won't be as chewy and cakes won't be as tender as if you used bread or cake flour.
Pastry flour is also a mix of hard and soft wheat flours with an emphasis on soft. Generally, the gluten content is 9-10% and is often recommended for pie crusts.
So, again according to The Fresh Loaf:
Then if you're interested in the details of the math, start out with a formula like (100parts/100parts * 7.5%) + (Nparts/100parts * 75%) = 10.5% [or 9.5% or 12.5% or whatever your desired result is], then solve for N. Skipping intermediate steps, simplification gives N = ((end-percentage-goal * 100) - 750) / 75 (Even this math is actually an oversimplification that's not quite right. It takes the not-quite-correct shortcut of directly adding percentages without accounting for the total being more than 100 grams. Hopefully though it's "good enough" ...)
The bottom line is: for every 100 grams Maida, add somewhere between 2.6 and 6.6 grams GlutenPowder. Adding 2.6 grams GlutenPowder will give a result with about 9.5% gluten, adding 4 grams GlutenPowder will give a result with about 10.5% gluten, and adding 6.6 grams GlutenPowder will give a result with about 12.5% gluten.
According to the original author of this answer, "You might find that bread and cakes made with maida don't keep as well as the same things made with all-purpose flour, but home baking never stays around for more than a day in my experience."
Whole wheat flour is denser, has more protein and tends to dry out products. To compensate, sift more, do not overmix, and up your wet ingredients slightly. From eHow. TLC confirms that whole wheat flour is higher in protein because it is milled from hard wheat which is naturally higher in protein, and then ground whole wheat flour is 25% higher in protein than all-purpose flour.
Some sites (including TLC) recommend only subsituting out up to half of white flour with whole wheat, except if you're using white whole wheat flour (see below).
My secret weapon is white whole wheat flour, which is lighter than standard whole wheat flour and tastes more like white flour but has the same health benefits as the whole wheat flour we're used to. Because so many people are looking for whole wheat recipes, you may want to try a recipe that is specifically designed for whole wheat flour--both for taste and texture. Try King Arthur Flour for recipes (they make my favorite white whole wheat flour, and they have a recipe for whole wheat biscotti!).
Best Answer
There has been quite a bit of confusion here concerning maida (which can be labeled all-purpose, especially in India). The top answer on the question that you linked to was actually incorrect. It has been fixed. Maida is actually a very low protein flour, much like what would be called cake flour in the US. I suspect and would appreciate if you can confirm that your use of the term "all-purpose flour" stems from the Indian use of the term, not that your recipes call for what Americans would call "all-purpose flour".
In answer to your question, yes, you can substitute what you know as white flour and what I know as all-purpose flour (`10.5% protein) for maida by replacing some of the white flour with cornstarch or potato starch. The best reference I could could find for the percentage of protein in maida was The Fresh Loaf, they say that, on average, maida contains 7.5% protein. To get from 10.5% protein to 7.5% protein, you would need to "lose" 3 grams of protein per every 100 grams of flour. By replacing 28.6 grams of white flour with potato starch or cornstarch, your mixture would have the the 7.5% protein content of maida. That looks good on paper, but my gut says to split the difference. I'd first try a mixture of 15 grams of potato or corn starch and 85 grams of white flour as a substitute for 100 grams of maida. The use of cornstarch in that way is commonly done in the US with our all purpose flour to emulate our low protein cake flour. cake flour with corn starch
In case the international flour terms aren't complicated enough, I understand that in Israel what is generally called cake flour has added leavening agents, it's like what I would call self-rising flour. Confused yet? I'll repeat here what I said in comments above: