我在预览中打开了一个 PDF，并尝试搜索一个短语，而不是仅仅搜索与搜索框中的内容完全匹配的字符串，而是分别搜索每个单词，我可以在文本周围加上引号，但如果您省略部分单词，则此方法不起作用。
下面是一段文本，搜索结果显示了我的意思。
It is known that there are an infinite number of worlds, simply
because there is an infinite amount of space for them to be in.
However, not every one of them is inhabited. Therefore, there must
be a finite number of inhabited worlds. Any finite number divided by
infinity is as near to nothing as makes no odds, so the average
population of all the planets in the Universe can be said to be
zero. From this it follows that the population of the whole Universe
is also zero, and that any people you may meet from time to time are
merely the products of a deranged imagination.
预览中的搜索结果：
infinite - 2 results (good)
finite - 4 results (good)
finite number - 7 results (should be 3, it is searching for each word separately)
finite numb - 7 results (same as above)
"finite number" - 3 results (good, includes 'infinite')
"finite numb" - 0 results (what?)
TextEdit 中的搜索结果（我希望从预览中获得的内容）：
infinite - 2
finite - 4
finite number - 3
finite numb - 3
"finite number" - 0 (quotes are treated as part of the search term)
"finite numb" - 0
当您搜索特定字符串时，此搜索对于大型文档毫无用处，您要么得到数百个结果，要么一无所获。（我确信它曾经有效，但有些东西已经发生了变化）。
这背后有实际的逻辑吗？我可以像 TextEdit 那样进行预览搜索吗？
我在用：
Preview Version 8.1
OS X 10.11.5
编辑：总体而言，搜索发生了什么变化？当我从 Safari 搜索此页面时，我再次得到了不同的结果：
infinite - 2
finite - 2
finite number - 2
finite numb - 2
"finite number" - 0
"finite numb" - 0