I get the feeling you're not looking for a pickle. What do you intend to do with the finished product?

There are a number of mango jam, salsa, pickle and chutney recipes available but the only way I know to preserve pumpkin besides pickles is to pressure can them in cubes.

We didn't used to cubes the pumpkin, but after loosing several jars (myself) and then the guidelines also changed after I discovered the same.

Decades ago, we BWB everything, but then many people became sick and lost lots of work due to processing that wasn't enough. I remember canning green beans in a BWB for 3 HOURS and am glad not to do that anymore.

My advise, if you don't want to possibly make people sick/die OR waste lots of time and effort.......follow the newer guidelines.

Does anyone have experience in acidifying vegetables to make them suitable for boiling water canning?

Yes, it is called pickling.

Anything can be pickled in 5% vinegar and BWB processed - including pumpkin and/or mango - and as indicated above there are recipes for doing it. But they are usually mixed with more traditional pickled items for an acceptable end taste.

Plus the amount of vinegar used is crucial and the processing times in BWB can vary a great deal.

Dave

Here is a link that might be useful: Pickling guidelines and recipes for fuits and vegetables

The old idea of canning vegetables with some limited amount of vinegar to ensure suitability for BWB canning has long been discredited. A small amount of vinegar is insufficient and a large amount, as already mentioned, turns it into a pickle.

Carol