Chinese contingency plan for the collapse of North Korea has made waves in the English language news media. While the authenticity of the document has not been confirmed (and perhaps should be questioned more seriously), its significance if authentic is an interesting question. There seem to be two likely scenarios if this is the case: we have learned interesting details about Chinese plans for North Korea's collapse, or the leak was an intentional message to the government of Kim Jong-Un about its role in China's international policy. It is worth noting that the two are not mutually exclusive.
If taken as a legitimate leak and not an intentional message, the plan holds few surprises. Military planners worldwide have long developed contingency plans for nearly every conceivable scenario (such as the infamous War Plan Red), so that China has developed a serious plan for the collapse of the North Korean state should not come as a surprise. The Chinese priorities in regards to North Korea have long been "no war, no instability, no nukes," and historically the best way of meeting these priorities has been supporting the Kim family regime. That the PLA will not invade North Korea to prop up the government should come as no surprise, as doing so would risk escalation into war with the United States. Rather, the plan calls for China to attempt to stabilize the situation as best as possible, including capturing North Korean leadership to prevent them from working against Chinese interests; presumably those interests are to prevent further instability or escalation into open conflict.
A more interesting possibility is that the leak was a deliberate message to Kim Jong-Un's regime. Assuming the document is legitimate, this seems a distinct possibility, as Chinese national security personnel do not have a long history of leaking classified government documents. If this is the case, the message is very clear: China is not happy with events in North Korea, and the preservation of the Kim regime is not a red line for the Chinese. There have been numerous changes in key leadership positions within the North Korean government which seem to indicate a power struggle has been underway, though it is unclear whether Jong-Un is consolidating his grip on the government or being sidelined to figurehead status. If China is sufficiently concerned about the DPRK's stability to leak military plans to the Japanese press, the rest of East Asia should certainly take the matter very seriously themselves.
This of course is all assuming the documents are legitimate, which is far from assured. While Kyodo News is a respected organization, the original documents or any information about the source has not been forthcoming. Furthermore, while the leak of internal Chinese material is not without precedent, the state's security apparatus has yet to produce a Daniel Ellsburg or Edward Snowden. As a result, while the plan is worth thinking about, it should be viewed much more dubiously than many Western media sources suggest.