Can the readings be wrong?
Yes. Readings are chosen by the pinyin-pro dictionary library from a word dictionary and the surrounding characters, and common trouble spots (还 hái/huán, 得 de/děi, 地 de/dì, the neutral tone in 看看) are corrected with rules on this page. They are checked against about 800 common words and short sentences, but unusual phrasing and long sentences can still be misread. Characters with more than one reading are underlined; press one to choose the right reading.
Does it work with traditional characters?
Yes. Traditional characters are mapped to simplified ones to look up the reading, and the text is shown as you entered it. Characters that also exist in simplified Chinese with a different use (such as 乾 and 著) are not mapped and may get the wrong reading (乾燥 → qián zào, 穿著 → chuān zhù; correct: gān zào, chuān zhuó). Underlined characters can be corrected with a click. Where the standard reading differs between Taiwan and the mainland, you get the mainland (Putonghua) reading.
The tone of 一 or 不 differs from the dictionary
一 and 不 change tone depending on the next syllable (一个 yí gè, 不对 bú duì). By default the dictionary tones (yī, bù) are written; turn on “Show tone changes of 一 and 不” to write the changed tones. The third-tone change (你好 is pronounced ní hǎo) is not written in either setting.
Which number is the neutral tone?
The neutral tone is written as 5 (们 → men5). Some dictionaries and input methods use 0 or no number instead.
What does printing include?
“Print” prints only the text with pinyin above the characters, without buttons or settings.