Nosah of N’phillath Apayim

Is it obligatory to say the entire tachanun as printed in the siddur?

Nefillat Apayim is on the one hand a hovah (obligation), yet the individual may choose what the content will be. Essential elements of nefillat apayim are pesukim (verses) which relate to techinnah (supplication), selichah (request for forgiveness), and vidui (confession). It is important to note that the Breslov concept of hitbodedut (personalized prayer) is an essential aspect of nefillat apayim. One should insert at least one or two lines of either personal or national requests.
In line with the above, there is no obligation to read the whole text of the nefillat apayim as it appears in the siddur. One may say a few lines of what is printed and then immediately afterwards add a line or two of request.