Adobe Acrobat new is better or worse

I’m working with OpenXml format of office 2007, so I keep the reference document open because I constantly need to search information into the document. The reference document is a 5200 huge 37 mb pdf, when I open it in Adobe reader 8 the acrobat process uses 60MB of ram, when I start a search of a text the search is incredibly slow, acrobat begin to use more memory. To make a comparison I try to search the text youcannotfoundThis and after 30 seconds acrobat is still at page 500, and the memory consumption is 125 mb.

Then I goes into this site and downloaded the version 4.05. With this really old version of acrobat reader I open the document, and did the same search for word youcannotfoundThis, the result is that it reach page 500 almost immediately, so it is really faster than the latest version, but after 10 seconds it reaches page 2500 and the search become really slow, about 10 pages for every second. The memory consumption is really low, around 20 mb, but I cannot search after page 2.500 because the search speed drops almost to zero.

I tried acrobat 5.05, it is slower than 4.05, but still much faster than 8.0, but again when it the search reach page 2.500 it hangs again. in 30 seconds the search reachs page 2.300 so it is faster than 8.0. Memory consumption is 22mb, but after page 2.500 search speed still drops to zero. When I open the document acrobat 5.05 tells me that the document use some newer features of pdf, so I need to use the latest version of the reader.

Then I check acrobat site and verify that the latest version is the 9.0, I download it and try again to open the document, same stuff, is a little faster than 8.0, but in 30 seconds the search reached only page 650.

I really dislikes this, I think that the average user uses acrobat reader to open, read, search and print documents, and all these features are supported by 4.0 version. I really does not know the newer features of the latest versions, but the only thing that I notice is that newer versions of acrobat reader are really slower. I think that it worth nothing adding new features if the old basic ones become less usable. Now if I search a term that have the first match in page 2000 I need to wait almost two minutes for acrobat to find the match, while version 4.0 found it in 17 seconds. I prefer adobe to take 4.05 version and make it not hang with the new version of pdf instead of making newer and slower versions.