1. Firstly, need to check which version pcl you need to install on your ubuntu system.

PCL download link:

https://github.com/PointCloudLibrary/pcl/releases?page=2https://github.com/PointCloudLibrary/pcl/releases?page=2

 Then click Assets, and download the source code.zip

2. unzip source_code.zip

3. cd source_code

4.

mkdir build && cd build

5. 

cmake ..

6.

make -j2 && sudo make install

7. 

please enter into /usr/local/include

the pcl-1.9 can be found here.