Annotating scatter plot in groupby plot

I have a df like so:

ID    Prcp   NDVI   Year
1     1.4    0.1    2000
1     2.3    0.4    2001
1     4.4    0.8    2002
1     0.4    0.1    2003
2     2.1    0.6    2000
2     1.2    0.4    2001
2     3.4    0.7    2002
2     2.8    0.5    2003

and I want to do a scatter plot of Prcp vs. NDVI for each unique ID. I then want to add a data label for Year for each particular point on the plot. I am trying to do it like this:

import pandas as pd
import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages

df=pd.read_csv(r'H:my_file.csv')
with PdfPages(r'H:path_to_outout.pdf') as pdf:
        for i, group in df.groupby('ID'):
                plot = group.plot(x=['Prcp'], y=['NDVI'], title='NDVI_' + str(i), kind='scatter').get_figure()
                n=df.Year
                b=df.Prcp
                c=df.NDVI
                for i, txt in enumerate(n):
                    plt.annotate(txt, (b[i],c[i]), fontsize=2.5)
                plt.legend(loc='center left', bbox_to_anchor=(1.0, 0.5))
                ax = plt.gca()
                ax.set_xlabel('Precipitation')
                ax.set_ylabel('Mean NDVI')
                pdf.savefig(plot, bbox_inches='tight', pad_inches=0)  
                plt.close(plot)

but this doesn't work correctly.

To do this for just 1 plot, with a df like this:

 ID    Prcp   NDVI   Year
    1     1.4    0.1    2000
    1     2.3    0.4    2001
    1     4.4    0.8    2002
    1     0.4    0.1    2003

I would do it like this:

a=df.Prcp
b=df.NDVI
n=df.Year
with PdfPages(r'H:graph.pdf') as pdf: 
        plt.title('NDVI')
        plt.xlabel('Prcp')
        plt.ylabel('NDVI')
        plt.scatter(df.Prcp,df.NDVI, facecolors='none', s=20, edgecolors='b')
        for i, txt in enumerate(n):
            plt.annotate(txt, (a[i],b[i]), fontsize=2.5)
        axes=plt.gca()
        fig=plt.gcf()
        pdf.savefig(fig)
        plt.show()