If you are asking how to officially get your site unblocked then the answer would be to get in touch with the appropriate government department to propose having your site unblocked. Presently the Pakistan internet filter is managed by the Pakistan Telecommunications Authority so they would be the best port of call to enquire about the unblocking.
If you are asking about how to bypass the block then it gets into a harder area as bypassing the block is an ongoing battle as the government finds your proxies and blocks them as well. I should also point out that there is a high likelihood that attempting to bypass the block could be a violation of Pakistani law and so you should seek proper legal advice as to all possible ramifications. Intellectually all you really need to do to bypass your site block in Pakistan (which presently uses URL based filtering) is to present your content on alternate URL's such as having alternate domain names as aliases for your site. The other option would be for users to access your site through some of the myriad of free and paid for proxy services online, some of which are entirely web based and many of which are VPN based (with VPN being more secure and more reliable though needing client side configuration), the key advantage from your point of view as a webmaster though would be the fact that you are not actively attempting to do anything to bypass the filter, instead it is up to the individual users whether they attempt to bypass government controls or not.
A common method used by some users is to use the TOR project to bypass government filters by tunneling out over the TOR network and using an exit node which is in a non-restricted country to gain access to your site, and as long as you are not blocking access to your site from TOR exit nodes then the end users can still access the site.
I should add here that nothing in this post is about the positives or negatives of government internet filtering, as filtering is a fact of life for many countries around the world, rather it is a look at the technical aspect of gaining access in spite of a filter.