Formulas fall apart when you copy them out of a PDF
You select a formula in a paper or a specification, copy it, paste it into Word — and the exponents drop to the baseline, the numerator and denominator of a fraction land side by side, and the radical sign is left stranded on its own. Retyping it usually takes less time than repairing it.
The cause is that a PDF holds no structure for a formula. Its contents are instructions: "draw this glyph at these coordinates". The bar of a fraction is a drawn line; an exponent is only a smaller glyph placed a little higher. Nothing in the file records that one is a fraction and the other an exponent. Copying picks the characters up in drawing order, and that is where the vertical relationships go.
So the formula has to be read back out of the layout. PDFIntact finds the formula blocks and writes them out in LaTeX notation, exactly as read, into Word, Markdown and JSON. Excel is not among them: an Excel export contains tables and charts only.
Try it now
Check it on your own PDF
The check runs entirely inside your browser. Your file is never uploaded, and no account is needed. See how many pages, and how many tables and figures, can be extracted before you pay.
Example
数式はこの形で書き出します
下は実際の論文PDFから取り出した数式です。数式のブロックは記法を剥がさず、そのまま残します。本文や表に紛れ込んだ上付き・下付きの記法だけは、読める形に直してから書き出します。
$$ \boldsymbol{y}(k)=\sum_{i=1}^{P}A_{i}\boldsymbol{y}(k-i)+\boldsymbol{e}(k) $$形式ごとに、どう入るか
同じ数式でも、書き出す形式によって入り方が違います。
Word（.docx）
読み順のその位置に、等幅の段落として入ります。Wordの数式オブジェクトにはしません。
Markdown（.md）
本文の流れの中に、記法をそのまま置きます。
JSON
種別「数式」・ページ番号・ページ内の座標つきで、書き換えのない値が入ります。
Excel（.xlsx）
入りません。Excelに書き出すのは表とグラフだけです。
Frequently asked questions
- Why do formulas fall apart when copied out of a PDF?
- Because a PDF does not store a formula as a formula. The bar of a fraction is a drawn line and an exponent is a smaller glyph placed slightly higher, with nothing in the file saying which is which. Copying reads the characters in drawing order, so the up-and-down relationships are lost.
- Which formats can formulas be exported to?
- Word, Markdown and JSON. The formula blocks keep their LaTeX notation exactly as read. Excel is not among them, because an Excel export contains tables and charts only.
- Do formulas become editable equations in Word?
- No. They arrive as text in a monospaced paragraph, in the position they occupy in the reading order, with the notation intact. We do not convert them into Word equation objects.
- Are the values in a formula ever estimated?
- No. Estimating a value from a shape is something we do for charts without printed numbers; formula blocks are not put through it. What was read is what comes out. Check the output against the original PDF all the same.
Check any PDF against all symptoms／ What each format contains