why can't i add signature to pdf

Keyword Analysis

Keyword	CPC	PCC	Volume	Score	Length of keyword
why can't i add signature to pdf	1.48	0.3	2896	94	32
why	0.12	0.6	8143	66	3
can't	1.08	0.7	7847	55	5
i	1.54	0.8	4206	70	1
add	0.89	0.5	4271	19	3
signature	1.9	0.4	2041	53	9
to	0.5	1	7303	81	2
pdf	0.61	0.4	1606	95	3

Keyword	CPC	PCC	Volume	Score
why can't i add signature to pdf	1.17	0.2	968	65
why can't i add a digital signature to a pdf	0.07	0.8	590	55
can i add signature to pdf	1.07	0.3	8927	50
unable to add digital signature in pdf	1.92	0.5	586	93
add signature to pdf without adobe	1.3	0.4	6350	86
how to add pdf signature	1.57	0.6	5248	6
pdf not allowing signature	0.97	0.2	4936	36
adding signature to pdf without adobe	0.51	0.4	1942	82
pdf signature not working	1.36	0.3	3498	28
adobe pdf not allowing signature	1.98	0.8	6437	58
pdf doesn't have signature option	0.56	1	7868	47
signature not showing on pdf	1.76	0.3	7689	96
signature doesn't show up on pdf	1.59	0.3	8329	83
adobe pdf signature not working	1.53	0.4	4790	12
digital signature not appearing in pdf	0.06	0.4	1755	70