This is a moderately common technical term which hasn’t yet reached any of the standard dictionaries I’ve searched, though the Second Additions Volume of the Oxford English Dictionary cites a first use as long ago as 1983. Upskilling refers, as you would expect, to increasing the skills of workers, usually through training. But its introduction reflects substantial changes in the nature of work in developed and developing countries. In the past two decades a substantial proportion of all jobs have become more technical and varied. Much of this is due to the introduction of computers, which require many workers to take on tasks like word-processing or financial analysis which once would have been done by specialists. Trainers and employers both argue that to upskill workers improves their employability. But critics say that upskilled workers are not necessarily better paid, nor do they have better promotion prospects, and that upskilling benefits the employer rather than the worker. Upskilling may be distinguished from reskilling, which usually refers to giving people new skills to cope with a new job, usually an enforced one.
Business Process Reengineering can result in more upskilled work and more integrated and interesting jobs, but upskilled work doesn’t necessarily mean better wages and promotional possibilities.
Scandinavian Journal of Information Systems, Vol 8, No 2, 1996
Measures to promote upskilling and lifelong learning can raise the mobility and employability of workers, mitigate the costs of job displacement resulting from rapid technological change and reduce resistance to reform.
Structural Reform and Adjustment, OECD Report (1998)